GTA
All Springer/NP/PCP Air Gun Discussion General => "Bob and Lloyds Workshop" => Topic started by: rsterne on February 21, 2014, 12:56:57 AM
-
I got my FD-PCP in the mail today, filled it to 1500 psi and shot a few strings with JSB 14.3 gr. Express.... I had a few teething troubles, the first of which I never did fully figure out.... The first string was great, high 800s, about 9 shots within 4% ES ending at 1500 psi.... I tried another string, didn't change anything, and the string started in the high 700s, with the first 6 shots way to slow to include in the string.... The next string was even slower, so I figured something had to be changing.... I knew the trigger could alter the velocity and when I checked it, it wasn't fully back (and the screws not that tight, it may have slipped forward), so I reset it fully aft, and while I had it off did a quick trigger tune, as the stock setting was horrible, the sear engagement was wayyyyyyyyyy too long and therefore creepy.... I shortened up the sear engagement to about 1/16", clipped 2 coils off the trigger spring (the adjusting screw was nearly falling out), and it was much improved.... With a bit of polishing it should be every bit as good as the QB trigger it is based on.... Incidently, this trigger uses the spring-loaded 2-piece blade like the ARs, so it has a 2-stage feel to it....
Anyway, with the trigger fully back, the gun wouldn't cock, the bolt slot wasn't quite long enough, so I had to move the trigger ahead about 0.020" and then it was fine.... The next string duplicated the first, so I thought I had found the problem, but the next string was once again slow.... and now I knew nothing was moving.... I found that the set screw in the bottom of the striker was loose, as was the slotted screw under it, and I tightened those and proceeded to find out what changing the preload would do.... I was curious if there was enough adjustment to get to coil bind, so I removed the lock nut and washer from the preload adjusting screw and wound the screw in until it was flush with the threaded plate, and the gun would still cock, no coil bind.... I filled to 1500 and shot a couple of shots, just over 940 fps which is 28 FPE.... Pretty impressive performance, I have to say, this thing must breathe pretty well.... I then started backing out the preload and recording the velocity, filling to 1500 each time, and the gun was solidly on a plateau, I had to back the preload out 5 turns before it even started to loose velocity.... I can only imaging what an air hog it would have been with the screw cranked in flush.... Anyway, at 6 turns from flush with the plate (which I took to be the maximum usable preload), I reinstalled the washer and lock nut, and the screw was flush with the surface of the nut when the slot was vertical, and the velocity was just beginning to drop, so I used that as a starting point for further preload testing.... As I backed off the adjusting screw so that it protruded from the lock nut, the velocity dropped rapidly, and at 3 turns out it was under 500 fps.... This is with the trigger as far back as I could get it and still cock the gun.... I graphed the results, and then proceeded to shoot some strings.... Here are the graphs.... NOTE: PELLET WAS 14.3 GRAIN, NOT 15.9 GRAIN !
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/FD_PCPStock_zpse5be9fb0.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/FD_PCPStock_zpse5be9fb0.jpg.html)
With the screw flush with the surface of the lock nut the gun was shooting right at the top of the sweet spot, but only got 6 shots before the velocity dropped more than 4% below the peak.... So, for my gun at least, there is no point in going for any more preload at 1500 psi.... At 1 turn out, I got a beautiful string of 9 shots, starting right at 1500 psi and ending at about 1100.... The efficiency was very good at 1.15 FPE/CI, and the string started out fairly quiet and by the end it was really loud.... At 2 turns out from flush with the locknut, the first shot was only 646 fps and really quiet, and the velocity gradually built until I could start counting shots at about 1350 psi, and the string ended at 1000 psi.... In other words, if you are using the recommended 1500 psi fill, all the usuable adjustment range (at least on my gun), with the trigger set back as far as you can and have the gun cock, occurs from where the adjusting screws is flush with the lock nut to about 2 turns out from there.... Since the adjustment is so sensitive, and I'm sure there are differences between hammer springs and other parts (not to mention trigger position, which makes a huge difference) the only way to determine this for your gun is to basically duplicate my testing method.... Keep cranking in the preload until the velocity plateaus, and then you know how far is too far, back it off until the velocity starts to drop, and then a bit further until you find your best tune....
My initial conclusions are that this gun is a powerhouse; my best string of 9 shots, from 1500 psi down to 1100, averaged 24.7 FPE at an efficiency of 1.15 FPE/CI.... I think the biggest challenge is going to be figuring out how to get a longer shot string within a 4% ES.... I'd like to set this gun up as a Grouse gun for my son, as a repeater using the MRod mags, and the ideal would be 20 shots (2 magazines) at 20 FPE with 18.1 gr. JSB pellets, which I know to be a deadly combination on Ditch Chickens.... I have a feeling that to accomplish that, I will have to restrict the porting somewhat to flatten out the shot string and increase the usuable pressure range beyond its current 400 psi....
Bob
-
Here is a photo of the Flying Dragons PCP, which is based on the XS-60C.... Mike installs a longer reservoir plus a fill fitting....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/9917e715-d1c7-4ba8-8707-9635a0174b7f_zps05f27958.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/9917e715-d1c7-4ba8-8707-9635a0174b7f_zps05f27958.jpg.html)
Here are some photos with the stock removed....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/IMG_4133_zps28847d9e.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/IMG_4133_zps28847d9e.jpg.html)
The angle bracket at the back has the screw that holds the back of the action in the stock....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/IMG_4125_zpsbb831043.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/IMG_4125_zpsbb831043.jpg.html)
The trigger is basically a QB/AR unit with the spring-loaded trigger blade and has the same adjustments.... I shortened the trigger spring 2 coils as the adjusting screw was nearly falling out when a suitable pull was achieved.... There is a slot in the read of the trigger guard, and a movable block that the front trigger screw threads into, which allows the trigger to slide fore-and-aft.... This changes the position of the sear, and hence the hammer travel and preload, drastically changing the hammer strike.... On my gun, when I moved it back all the way, the bolt wouldn't come far enough back to cock the gun, so I ended up with it about 0.020" forward of the back position....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/IMG_4127_zps550d9d00.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/IMG_4127_zps550d9d00.jpg.html)
There is a spring inside the bolt, when you remove the screw and pull out the handle, ahead of that is the spring, don't lose it!.... The rear block that mounts the velocity adjuster has two screws one on the bottom and one on the side, and once removed and the screws are removed from the bolt and striker, everything slides out the back (so I understand).... I haven't had them or the valve out yet, I'll add pics when I do....
Bob
-
Wow, a lot of great info. You explain it very well. Need to make a sticky out of this so it is easy to find. Thank you.
-
thanks for the 1 2 3 Bob
-
I completely disassembled the FD-PCP today, and did some measuring.... First of all, here are the parts.... You can pretty much tell from the photo where everything goes....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/IMG_4136_zps307c82a1.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/IMG_4136_zps307c82a1.jpg.html)
Here are a few observations about the construction, and some comments about the safety of the design....
1. The fill fitting has an internal check valve, there is no check valve inside the male Foster.... The means you can't use a "T" and install a gauge where the Foster is, it won't read the gun's internal pressure once the check valve closes.... The O-ring that seals the fill fitting is located in the threaded portion of the tube, so part of the threads are pressurized....
2. The back of the tube threads into the receiver.... There are lots of threads, so the shear strength isn't an issue, even though the receiver is aluminum of unknown quality, I wouldn't worry about that.... However, the tube seals at the inner end against a square-section O-ring which sits against a shoulder flush with the front of the valve.... As such, the threaded area of the tube is pressurized....
3. I measured the threads, and they appear to be 22mm OD x 1mm pitch.... While I couldn't find a listed diameter at the bottom of the thread groove, using the standard formula for Metric threads with a 1mm pitch, the diameter should be at least 20.6 mm (0.811").... The inside diameter of the threads in the receiver is 0.827", so the OD of the structural part of the tube certainly has to be smaller than that.... The ID of the tube is 0.745".... I do not know the material the tube is made from, but using 1010 mild steel (44K yield, 53K tensile), I get a pressure to yield of 3900 psi, and 4700 psi to burst.... At the 1500 psi recommended fill pressure, that works out to a 2.6:1 safety margin to yield.... If the threads are shallower, or the material is stronger, then that increases....
4. The valve is located by two 5mm x 0.8 mm steel screws of unknown quality in shear.... Since one of the load-bearing screws is in the steel block behind the valve, is it critical that the valve bear tightly against that block, otherwise only the valve screw would be taking the shear load.... I would highly recommend that when you have your gun apart that you check that, and if they are not in firm contact, add a thin shim between them to insure both screws are doing equal load bearing.... The threaded portion of the screw is subject to the shear load, so I used the minimum listed minor diameter and calculated a total shear force of 1154 lb.f. for the two screws, assuming 1010 mild steel with a 53K tensile strength (32K in shear) .... With a 0.745" ID for the reservoir, at 1500 psi, the load on the valve is 654 lbs. which means the safety margin is 1.8:1.... If the screws were upgraded to high-tensile screws, this would increase, and I would highly recommend that anyone contemplating using more that the recommended fill pressure confirm that the screws are up to the job.... Where the valve screws penetrate the receiver, you could see faint marks from where the threads of the screws were pressing on the back of the hole.... However, the material is thick enough that I was not concerned about the bearing load at the recommended 1500 psi, but it is something to keep an eye on each time you have the gun apart....
5. I noticed that the valve stem only protrudes 0.100" from the back of the steel supporting block.... That limits the valve lift to that distance, although the poppet itself is capable of much more.... I have not measured the actual lift in the FD-PCP, but it would not surprise me that the striker is hitting the block at the low pressure end of the shot string.... This is not likely the case in a properly adjusted shot string at the high pressure end, because the valve is achieving self-regulation.... but it could result in the right hand (low pressure) side of the shot string dropping off quicker than it should if there was more lift available.... This may be the reason for the very limited (approx. 400 psi) pressure range I was seeing between fill and refill when restricting the string to a 4% ES.... I am going to machine 0.050" off the back of that block to allow more lift before I reassemble my gun to confirm this theory.... I have already determined that it is possible to take off 0.080" and still have the striker hit the block without the pin hitting the end of the cocking slot in my gun....
6. I measured the porting on this gun, and to be frank, IT'S HUGE !!! .... The valve throat is 0.205" and the stem is 0.118" giving an equivalvent diameter for the throat of 0.168".... The exhaust port on the valve is 0.195", and the port through the receiver is the same.... The barrel port is 0.162", which is right at the recommended maximum for a .22 cal bore.... About the only thing I can see where you could possibly improve the flow would be to drill out the throat slightly to 7/32" (0.219") and round off the transition between the throat and the bottom of the exhaust port.... No other changes would be necessary for .22 cal, IMO, and in fact the valve is capable of being enlarged to flow well for a .25 cal by increasing the throat to 15/64" and angling the port with a 3/16" mill.... A 3/16" barrel port for the .25 cal barrel would complete the changes.... I did notice that the barrel port was slightly forward of the hole in the receiver, although not enough to shroud it, but if you were building a .25 cal you would want to make sure they lined up better....
In conclusion, the gun is pretty well made, especially considering the price point.... Like most guns, it can benefit from disassembly and cleaning, checking for burrs, and polishing up the hammer, sear, and trigger contact points.... and making sure that bolt functions smoothly, then reassembling with the proper lubes.... With the size of the ports, it is not surprising to see the power the gun puts out, but also not surprising to see the rather "peaky" power curve, which leads to a shorter shot count within a decent ES.... I have made a new fill fitting with integral gauge mount as shown below....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/IMG_4139_zps4d69d244.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/IMG_4139_zps4d69d244.jpg.html)
The O-ring is moved inboard of the threads, and it takes up less volume in the reservoir.... I added a check valve to the male Foster fitting....
Bob
-
Great thread Bob. Any idea of what the trigger pull is ?
-
Adjustable.... *LOL*.... I still haven't polished things up in that area....
Bob
-
Awesome work Bob, and thank you for posting the details of your work. Many of us are new to PCP and very much appreciate your willingness to share your information and experience. My next task is to smooth out my trigger. The current pull weight is too high and the feel is a little gritty.
-
I reassembled the gun tonight, and I don't see any difference with the back of the block machined off.... MAYBE one more shot within the 4% ES and able to use another 50 psi at the bottom end, but certainly nothing dramatic.... I'm going to have to figure out how to restrict the porting to flatten the curve and get more shots at reduced power.... My goal for this gun is 16-20 shots at 20 FPE if possible.... 18.1 gr. JSBs at 700+ fps is great Grouse medicine.... However, before I do that I'm going to hog out the valve just a touch first to see what easy gains are possible....
BTW, the new fll fitting worked perfectly, it's nice to have a gauge on the gun....
Bob
-
thanks for the infor Mr. Rsterne. please keep us in the loop about how restrict the transport. since the it is built into the receiver it will be interesting to see how you handle it.
-
This is getting to be very interesting. I might have to get one.
Bob, I was wondering how what is the potential for modding it. You mention that the ports are wide one for .22. I Wonder if it actual benefit from closing some of the power. Maybe this way you can shoot through a larger psi range, fatten the curve some and gain a few shots.
-
"4. The valve is located by two 5mm x 0.8 mm steel screws of unknown quality in shear.... Since one of the load-bearing screws is in the steel block behind the valve, is it critical that the valve bear tightly against that block, otherwise only the valve screw would be taking the shear load.... I would highly recommend that when you have your gun apart that you check that, and if they are not in firm contact, add a thin shim between them to insure both screws are doing equal load bearing.... The threaded portion of the screw is subject to the shear load, so I used the minimum listed minor diameter and calculated a total shear force of 1154 lb.f. for the two screws, assuming 1010 mild steel with a 53K tensile strength (32K in shear) .... With a 0.745" ID for the reservoir, at 1500 psi, the load on the valve is 654 lbs. which means the safety margin is 1.8:1.... If the screws were upgraded to high-tensile screws, this would increase, and I would highly recommend that anyone contemplating using more that the recommended fill pressure confirm that the screws are up to the job.... Where the valve screws penetrate the receiver, you could see faint marks from where the threads of the screws were pressing on the back of the hole.... However, the material is thick enough that I was not concerned about the bearing load at the recommended 1500 psi, but it is something to keep an eye on each time you have the gun apart...."
Very great point Bob!
As I would like to use a 2000-psi fill, especially after the valve tune, Jason B. was clairvoyant enough to realize stronger or better screws would need to be used, so he replaced the factory screws with high tensile strength screws.
So far, so good on the modifications!:)
The tube has been filled with 2000-psi for a week now with NO leaks at all!
Should have her back next week, can't wait!
Respectfully,
Al.
-
Impressed. Not just the performance of the rifle, but the detail in the write up.
-
Al, now that you addressed the screws so that you can increase the pressure, you have decreased the safety margin on the threaded portion of the tube.... Until we know what the material is, we have to assume mild steel, so at 2000 psi (using 44K to yield) you have reduced the safety margin to 1.9:1.... That means that every time you fill the tube you are "working" the steel past 50% of it's yield strength, which is into the area where fatigue becomes an issue.... Add to that the "stress riser" caused by the sharp vee at the bottom of the threads, and eventually I would expect the tube to fail at that point.... It might take 50,000 cycles, or it might not, and if the tube is CrMoly you might be just fine.... but exposing the threaded portion of the tube to pressure is the weak point of the design, IMO, once you address the screws....
Bob
-
Al, now that you addressed the screws so that you can increase the pressure, you have decreased the safety margin on the threaded portion of the tube.... Until we know what the material is, we have to assume mild steel, so at 2000 psi (using 44K to yield) you have reduced the safety margin to 1.9:1.... That means that every time you fill the tube you are "working" the steel past 50% of it's yield strength, which is into the area where fatigue becomes an issue.... Add to that the "stress riser" caused by the sharp vee at the bottom of the threads, and eventually I would expect the tube to fail at that point.... It might take 50,000 cycles, or it might not, and if the tube is CrMoly you might be just fine.... but exposing the threaded portion of the tube to pressure is the weak point of the design, IMO, once you address the screws....
Bob
Question/s: Is Co2 pressure any different than "air" pressure? When filling the tube with Co2, what is the minimum pressure and maximum pressure, or is it a constant?
I am asking because it is my understanding that Co2 can reach 1900-psi?
I am sure you can figure out what I am getting at here.
Please explain the differences, as this is a dual power source PCP.
Thanks,
Al.
p.s. There is a place here that tests metals, I guess I need to bring mine to them when it gets back to have the metal tested or send an e-mail to the Manufacturer and ask them? There are many who are venturing into filling beyond the 1500-psi range and I am sure that many more will want too, be nice to finally know what the deal is with the integrity of the metal. Is it weak and simply will not handle more than 1500-psi or is it strong enough and it will handle more than 1500-psi, in a safe manner?
-
Personally I would not go above the recomended 1500 psi, thats a risk I prefer not to test while holding it in my hands. Yes C02 can vary all over the board but ive never heard of it going over 12-1300 psi.
-
"About the only thing I can see where you could possibly improve the flow would be to drill out the throat slightly to 7/32" (0.219") and round off the transition between the throat and the bottom of the exhaust port.... "
As you explain better in more technical terms, this is the work that has already been performed on my FD-PCP valve; in addition to the Delrin stem or poppet. The measurements may not be identical, but we expect great results none the less! :D
Thanks,
Al.
-
Personally I would not go above the recomended 1500 psi, thats a risk I prefer not to test while holding it in my hands. Yes C02 can vary all over the board but ive never heard of it going over 12-1300 psi.
That's good to know, I was thinking I had read somewhere that Co2 could reach 1900-psi, must have misinterpreted that.
Assuming that Co2 can reach 1300-psi as a max, would there be a higher safety margin built into the design of the XS60C? A cushion if you will? If yes, what would that average safety margin be, not only for the XS60C, but for other Co2 air-guns as well?
Seems if they know Co2 can reach or peak at 1300-psi, they would make the parts be able to handle twice that amount?
Thanks,
Al.
-
The original XS-60C was designed for CO2.... Since that can be reached 1900 psi at 120*F, a prudent designer would design for a MSWP of 1900 psi and allow a safety margin well above that.... A perfect example is the CO2 tanks which go by weight.... They are rated at 1800 psi MSWP (used as the standard for CO2), and carry a 3K burst disc, as that is the pressure that they are Hydrotested to.... If out of date, you can't get them filled, they must be retested.... The XS-60C shares many features with the QB-7X rifles, including, presumably originally a tube that is 22mm OD x 1.5mm wall and therefore 19mm ID.... Even in mild steel (44K yield, 53K tensile), a tube of those dimensions would yield (start to stretch and not recover) at ~7000 psi and burst at ~8400 psi.... The tube Mike has used appears to be the North American equivalent size, which is 0.875" OD x 0.065" wall, which means it is larger on the OD and smaller on the ID (but only 0.003"), and hence stronger.... However, he then threads it to the same 22mm x 1.0mm threads as the stock gun, he has to so that it will fit the receiver.... So, now, assuming the tube is still mild steel of the same quality, the strength of the two tubes, at the bottom of the threads (the thinnest part) is virtually the same as it was before.... Now let's look at that part....
I couldn't find a spec. for the dimensions of a 22mm x 1.0mm thread (it's a bit of an oddball size) to the bottom of the thread, but there is a "Standard Metric Formula" for thread dimensions, and for a 1mm pitch on a 22mm thread, the diameter of the bottom of the grooves comes out to a mimimum 0.811".... assuming the threading was done to that standard.... If a die was used to produce the threads on the tube, that is a safe assumption, if it was done by "single-point" threading in a lathe, then there are two other variables, the depth of cut and the point on the end of the threading tool.... and those could cause significant variations between individual guns, with no way to calculate them, so I assumed that 0.811" measurement.... So, instead of using the 0.875" OD that Mike started with, or the 22mm (0.866" OD) of the original tube, we have to use that 0.811" OD when calculating the wall thickness.... Mike's tube is 0.745" ID, slightly smaller than the 19mm (0.748" ID) of the factory tube, so it picks up a tiny bit there.... but we are dealing with a tube (measured to the bottom of the threads) of 0.811" OD x 0.033" wall (instead of the 0.065" wall it started with).... That works out (using mild steel as above) to ~3900 psi to yield and ~4700 psi to burst.... for a safety margin of 2.6:1 at Mike's recommended 1500 psi.... Incidently, the original tube, at 1800 psi (recognized as the MSWP for CO2).... with it's slightly larger ID, and again assuming mild steel, is ~3700 psi yield and ~4500 burst, for a safety margin of 2.1:1.... This means that if it was subjected to a Hydrotest of 5/3 the working pressure, ie 3000 psi, it should pass.... at least once before there was any fatigue.... The screws, on the other hand, would be right at their shear limit, depending on the material they are made from....
So, we are in a situation not unlike a QB79.... The tube is plenty strong enough, but the holes for the tank block are too close to the end, causing a weak point that has been known to fail at 2600 psi when the stock is not in place, ripping the tank block from the end of the tube and nearly shearing off the stock (very soft) tank block screws in the process.... Like the XS-60C, it would appear on the surface to be plenty strong enough for 1800 psi, but when you look at the details, it comes uncomfortably close to failure at what would be the Hyrdotest pressure of 3000 psi for CO2.... I do not know if this is a cultural difference, but I have a gut feel that the lawyers in a North American firm such as Crosman would highly frown on pushing the design of ANY part of a pressure vessel to those limits.... Once you go to a safety margin of less than 2:1 with steel, you are guaranteeing that eventually fatigue will be a problem.... It becomes a matter of when, not if, a part will fail over time with repeated flexing (filling).... Even using a safetly margin of 3:1 isn't a guarantee that won't occur, because holes, threads, and imperfections in the steel itself lead to increased stresses in the metal (called stress risers) which even though the part as a whole isn't exceeding 50% of the yield stress, locallized portions are, and that can for cracks and lead to failure over time.... Like anything else in life, there are no guarantees, but it is prudent to hedge your bets, and not to exceed 50% of the yield strength of steel components to hopefully avoid fatigue failure....
Please realize that I intend no criticism here for Mike Melick.... He has used the same engineering numbers as were used on the stock XS-60C, which was designed for CO2 use, and in fact because his tube is 0.003" smaller on the ID, it is slightly stronger with the same external threads.... If he chose CrMoly tubing for the reservoir, then the safety margin at yield can be increased to 3.7:1 at 1500 psi, and it would be 2.8:1 at 2000 psi.... Likewise, if a thicker wall tubing was used (smaller ID), the safety factor would drastically increase, but of course a custom fill-fitting would be required to fit the smaller ID.... We are still left with the fact that without a valve screw upgrade that remains the most likely point of the gun to fail.... If you upgrade the screws, then the next thing to look for is the tops of the screw threads pressing dents into the aluminum receiver as the load will eventually exceed its yield strength.... Unless you really know what you are doing, I would strongly suggest you stick to Mike's recommended 1500 psi fill pressure.... I, for one, will not exceed it, and if I was going to build a bottle gun, I would make sure that the regulator had a 1.8K burst disc installed,, just like I would on a QB 7X....
Bob
-
Rdsail.... I will be trying a smaller barrel port in my gun, likely using soft solder to fill it and then redrill it.... You are correct, there is no "transfer port' in this design, just a 0.195" hole between the valve chamber and the barrel chamber.... The other alternative is to solder a smaller tube into the valve outlet, which may be easier to do.... As of yet, I haven't figured out an easily removable/replaceable way to do it.... but I WILL try a smaller port fairly soon....
Bob
-
This is more of questions than advice and as said before I greatly appreciate you being a member of this forum with you given knowledge.
I would think added screws either in the valve or striker block would help keep the receiver holes from elongating. Second your thoughts of the weak point of the threads on the tube. Do you think being that the threads are in the receiver that the receiver body would help with the holding the pressure? If not I would think if the receiver body cannot hold the higher pressure that no matter how strong the tube is a higher pressure would be a danger. Third if the barrel port was to be milled or drilled slightly bigger but not pass the original port hole that it would leave a lip to hold an insert for use of various port sizes. Anyway that's my thoughts.
-
Adding fasteners to the valve and/or the steel backing block would be an excellent way to strengthen that part of the gun.... I have already thought of milling a recess in the barrel so that an insert shaped like a grommet or rivet could be used to alter the transfer port size.... great minds think alike....
If you take a look a the tube where it exits the receiver, the threads extend past the receiver, so it adds no strength at that point.... You are correct that the receiver adds strength to the tube where it tube is inside it, but right where the tube could be stressed, as for example if you fell on the gun, is the weakest point.... at the bottom of the threads where the tube wall is only 0.033" thick.... With the stock fill fitting the O-ring is located in about the middle of the threaded portion, so the inner part of the threaded portion is under pressure.... That is a simple fix by redesigning the part, but it means Mike can't use stock parts, so I understand why he did that.... My gauge mount has the O-ring inside the threaded portion, so it is not pressurized, eliminating that problem at the front of the tube....
Bob
-
I just realized I made an error in the first post, the pellets I have been using for testing are 14.3 gr. JSB Express, not the 15.9 gr. Exacts.... I have corrected that post but the title on the graph is misleading.... my apologies for the error....
Bob
-
So with all the calculated theory one will never know the limitations of the fill pressure until tested. Someone did mention on taking on the task of doing a pressure test. I would think that there would be some mods done (one that a home tinkerer could perform) before testing. As for testing it does cost time and money. I would put in some money (send a partial payment to Mike for a prototype rifle) if the gun being tested was modded under rsterne's recommendations. So if anyone else likes to put money into this project the less I would have to invest :). If there are any volunteers let me know. It would have to be a reputable know member of the GTA for one thing I would think.
-
Today I did some mods to the valve, just to see what would happen, and where there might be some remaining restrictions.... I did this in two stages, first by increasing the flow OUT of the valve, and then by increasing the potential flow INTO it.... In the first stage I made the following changes:
1. I drilled the throat to 7/32"....
2. I used a 5/32" spherical burr in a Dremil to smooth the transition between the throat and the bottom of the exhaust port, where there was a sharp 90* corner.... I smoothed that out to ease the flow....
3. I tapered the sides of the brass poppet from the OD of the spring at the front to the stock OD (OK, I filed it down a bit!) at the back....
4. I bored out the inside of the back of the valve to 0.475" to increase the gap between that and the OD of the poppet from 0.035" to 0.050"....
I felt that these were the only places that the valve, with it's already generous exhaust port, needed any attention for a .22 cal gun.... When I tested the gun with the hammer spring preload maxed, I picked up 40 fps, which is not huge, but not insignificant either.... As expected, however I lost a shot or two in the shot string.... I then modded the front portion of the valve to make sure that wayyyyyyyy more air could get into the valve than it needed.... I was pretty sure this was a waste of time, as the valve already has slots to open up the flow, but I did the folowing:
1. I increased the slots from 5/32" wide to 1/4" and doubled their length....
2. I removed the washer that acts as a spring seat, and drilled a new 5/16" pocket in the end of the valve to hold the longer valve spring.... The spring is a shortened hammer spring from a Crosman 2200, but a shortened Disco hammer spring would work as well.... It is 1.5" long and 0.035" wire and has about the same seat pressure as the stock spring....
3. I drilled the hole in the end out to 15/64" (the ID of the spring)....
4. I used the Dremel to taper and round the edges left by the milling to ease the flow and reduce turbulencs....
Here is a photo of the modded valve....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/IMG_4141_zpsfb944500.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/IMG_4141_zpsfb944500.jpg.html)
As I expected, opening up the inlet side of the valve did almost nothing, it added 10 fps.... I tested the valve after the first (flow) changes and again after the second (inlet) changes, and plotted the velocity against preload with the following results....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/FD_PCPModded_zps433dc2cb.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/FD_PCPModded_zps433dc2cb.jpg.html)
I have a suspicion that the hammer spring is taking a "set" or that something else is changing, as the gun required more preload today before I started modding the valve.... Increasing the throat diameter of the valve may have required more hammer strike to reach the plateau, but I can't see how increasing the flow into the valve did that, unless it is "blowing" the poppet shut faster.... The important data is that there was a bit of a gain by improving the flow out of the valve, but very little to be gained by increasing the inlet area....
After these mods I played around to find the new optimum hammer preload with the 14.3 gr. JSB Express pellets used in the testing of the stock gun.... Here is the resulting string, from 1500 psi down to 1150....
942
975
976
962
953
934
Yes, only 6 shots within a 4% ES, that's what happens when you hog out the ports in a valve, you gain power but loose shots.... The efficiency was still decent, at 1.03 FPE/CI, but I had to refill at 1150 psi.... The average over the 6 shots was 957 fpe (29.1 FPE), a gain of 18% but a loss of 3 shots.... I then tested the gun with JSB 18.1 gr Heavies, with the following results....
879
890
910
915
909
895
880
I picked up one shot with the heavier pellets, plus a nice gain in power as well.... The average over the 7 shots was 897 fps (32.3 FPE) at an efficiency of 1.17 FPE/CI, filling to 1500 and refilling at 1100 psi.... This is a whack of power for a $100 gun with only a few minor changes.... especially considering the low fill pressure.... I am running out of adjustment on the preload, however, the screw is now halfway through the locknut, with no washer behind it....
Now that I have pushed the power about as far as I think it can go with a 1500 psi fill, I need to back off the power and start working on shot count.... This is where my previous experience with the Disco will hopefully come to the rescue.... This graph is my starting point....
(http://i378.photobucket.com/albums/oo221/rsterne/Discovery/2260DiscoPortFPE_zpsde9a4c6c.jpg) (http://s378.photobucket.com/user/rsterne/media/Discovery/2260DiscoPortFPE_zpsde9a4c6c.jpg.html)
That graph was done with a stock Disco barrel with a port of only 0.134".... That choked up the flow for the largest transfer port sizes, preventing it from continuing on up to the 30 FPE region we are getting with the FD-PCP with it's 0.161" barrel port.... If you look at where that would be on the Disco graph, it would pretty much mean a linear trend of FPE with transfer port diameter.... Since I want about 20 FPE, it looks to me I should be looking at a transfer port (or barrel port) diameter of about 7/64" (0.109").... I think that's as good a place as any to start....
Bob
-
I would not be willing to sign off on any design as the result of a single pressure test.... at least not if the calculated safety margins are low enough that I have any concerns about fatigue life.... All that a test would show is that that one gun is OK at the moment.... Besides, it's not really up to me, I'm not selling them.... Mike is using a commercially available CO2 rifle, not making anything weaker, and recommending it for 1500 psi, which is within the pressures that the rifle may see in use with CO2 on a hot day.... All I'm doing is cautioning people to listen to his recommendation and treat the rifle like what it is.... a modded CO2 platform.... I am NOT an engineer, just a concerned hobbyist with a bent for arithmetic.... I make exactly the same statements for a QB/AR.... If it's regulated use a 1.8K burst disc and set the regulator for 1500 psi maximum.... If it's not, just don't fill beyond 1500.... Either way, it's just my opinion....
Bob
-
Here is the first attempt at restricting the porting.... I found a small rivet that had a 0.104" hole in it and shortened it and glued it into the barrel port.... It turns out I still have a bit more power than I want.... I am looking for 20 FPE and got 23.3 FPE.... Here is the shot string, starting from 1500 psi, compared to without the port restrictor....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/FD_PCP18gr_zpsfb81b013.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/FD_PCP18gr_zpsfb81b013.jpg.html)
I'm back up to 9 shots, the same as I had at this power level when the gun was stock.... The efficiency has climbed to 1.25 FPE/CI, but to keep a 4% ES I can only use 350 psi, refilling at 1150 psi.... There has to be some way to flatten the shot string to be able to utilize a wider pressure range.... I'm contemplating the bstaley O-ring buffer....
Bob
-
I would not be willing to sign off on any design as the result of a single pressure test.... at least not if the calculated safety margins are low enough that I have any concerns about fatigue life.... All that a test would show is that that one gun is OK at the moment.... Besides, it's not really up to me, I'm not selling them.... Mike is using a commercially available CO2 rifle, not making anything weaker, and recommending it for 1500 psi, which is within the pressures that the rifle may see in use with CO2 on a hot day.... All I'm doing is cautioning people to listen to his recommendation and treat the rifle like what it is.... a modded CO2 platform.... I am NOT an engineer, just a concerned hobbyist with a bent for arithmetic.... I make exactly the same statements for a QB/AR.... If it's regulated use a 1.8K burst disc and set the regulator for 1500 psi maximum.... If it's not, just don't fill beyond 1500.... Either way, it's just my opinion....
Bob
Sorry Bob didn't mean to put it at a point where you would be signing off on anything. I just thought if I was to put money into a perfectly good gun to be blown up. I would like to know that it was done with any upgrades to maximize potential weak points. I am may be just to curious to know the outcome so I would feel safe if I was working at a higher pressure than 1500 psi. I guess a $100 PCP gun is what it is and a will live with that in a safe manner. Which I respect that is your main concern.
-
Was wondering how to get to 16-20 shots/20 foot pounds with that rifle.
Just took a WAG of the volume and ran some of the efficiency equations. Going to have to be an efficient set up to get up to 16-20 shots. Thinking the bstaley o-ring trick might be worth a shot.
-
I'm trying to duplicate my own Grouse gun.... It's 2260 based, and I get 16 shots at 20 FPE from just 65cc when filled to 2000 psi, shooting down to 1100, and that's with a 14.5" barrel.... Yes, it's VERY efficient, that works out to 320 FPE from 4 CI with a 62 bar drop with is 248 CI, or 1.29 FPE/CI.... Yes, this gun only fills to 1500 psi, but the reservoir is 77% larger (115 cc) and it has a 21.5" barrel.... I'm already getting 1.25 FPE/CI, the only thing holding me back from achieving my goal is the ridiculously small usuable pressure range of only 350 psi on that most recent 23 FPE string.... That is only 27% of the fill pressure, with my 2260 based gun (or a Disco) I can use 45% of the fill pressure.... If I can just get the usable pressure range up to 600 psi I'd be all set.... particularly once I drop the power down to the 20 FPE I want.... After all, from 1500 down to 900 is only 40%, surely that should be acheivable with a 4% ES ?....
Bob
-
Just have questions, wish I had answers.
But sometimes it helps to hear (in this case, see) the problem in a different light.
Problem is that it runs over a narrow pressure range. So what changes would (or "should") make it run over a wider range?
-
Well, I thought I just did that.... Usually when you make a gun breathe better, you increase the power but narrow up the bell-curve.... That is what happened when I increased the ports.... So then I fitted a tiny 0.104" port.... I lost quite a bit of power, but I only got back to where I started for shot count, and even less for usable pressure range (350 psi instead of 400).... To put it frankly, I'm perplexed.... This gun isn't acting "normally" to restricting the porting....
When I went from a 0.140" transfer port on my Grouse gun to a 0.125" I went from 14 shots over 700 psi to 16 shots over 800 psi, both at 20 FPE.... More recently, on my .30 cal Disco Double, I went from 6 shots at 118 FPE over 900 psi to 9 shots at 110 FPE over 1000 psi to 11 shots at 104 FPE over 1200 psi just by restricting the barrel port.... The total energy in a 4% ES string went from 713 FPE to 1146 FPE.... and all used the same 3000 psi fill.... I thought I understood this stuff, and then this gun comes along and throws a monkey wrench in the works....
Bob
-
The elusive beast, the “hellifiknow”.
We approach this from completely opposite perspectives. You are numbers guy and I just go by intuition. Am pretty much a hands-on visual learner (which means I generally screw up the first one before getting it right).
So my thoughts are these:
1. What’s different about this gun’s set up compared to other guns that followed the rules?
2. Whatever is unique to this gun must be the reason for it not following the rules.
3. Change it/make it conform to the other guns set up, and it will probably follow the same rules.
-
Could the extra back pressure be escaping through the two rear seals?
-
The biggest thing is it's only a 1500 psi fill.... Considering that, it also has big ports and flows air like mad, producing a lot of power from the low pressure.... I mean it's getting nearly 34 FPE at 1300 psi with 18 gr. pellets when tuned for a bell-curve that runs from 1500 down to 1100....
I can't increase the fill pressure, not safe to do so without significant changes, IMO.... I'm wondering if the valve spring is too heavy, it is comparable to a Disco in force, which is a higher PSI gun (with a bigger stem diameter as well).... I'll try that before attempting any other changes, using a shortened 2240 spring.... Reducing the spring pressure will increase the percentage change in closing force over a given pressure range.... and the effect will be more noticiable on a lower pressure gun because the spring is a bigger percentage of that force.... This effect is increased because this valve only has a 3mm (0.118") stem while the Disco is 0.156".... I'm thinking that a larger percent change in closing force may lead to a larger usable pressure range because the valve lift will change more over a given pressure range.... This greater change in lift should increase the valve's self-regulation, increasing the velocity more at the low end, right?....
Hmmmmmmmmmmm.... this may just be the answer, wouldn't THAT be nice.... not only to cure the problem, but one more piece of information to add to the tree of knowledge about PCPs.... Heck if a lighter spring doesn't work, then maybe heavier?.... *LOL*....
Kailua, I suppose that is possible, if that's the case then restricting the exhaust port in the valve instead of the barrel port would change that.... I would expect that if a significant amount of air was escaping I would either feel it, or the efficiency would decrease, and in fact it increased when I restricted the barrel port....
Bob
-
Perhaps the larger volume coupled with lower pressure is the culprit? Meaning, you can hold more air (versus 2260), but it is less dense. This could mean you need less air to produce the same amount of energy in the lower volume gun, which coupled with good efficiency means a better shot string. In other words, you experience a smaller pressure drop each shot and get better energy transfer the same time because the more densely compressed air of the smaller volume gun produces more useable energy each shot. The larger volume of the XS60 means you don't use more air, but pressure drops faster due to larger volume, so available energy drops as well. Another WAG assisted by Capt Morgan from a non pcp aficionado... ;D
-
Except that pressure drops slower because of the larger volume.... The volume governs the TOTAL shot count, but has little to do with the starting and ending pressures.... As an example, if you compare a 2260 tube to a Disco, to a Disco Double, all running the same pressures with the same valve, the shot count pretty much tracks in proportion to the volume, and the power is not much different, providing you're not talking over 50 FPE where the smaller tube would start having a slightly increased affect during a shot....
There is no question that a 2000 psi gun is more efficient than one running at 1500, just as a 3000 psi gun is more efficient than one running at 2000.... providing they are all set up for the same FPE levels.... That is simply because higher pressure air contains more energy per cc.... Getting the power isn't my problem, nor is getting good efficiency.... the problem is the very limited pressure range as a percentage of the fill pressure....
EDIT: In terms of the amount of total Potential Energy of the air in the tubes, the FD-PCP with 115 cc at 1500 psi contains 27-30 % more energy (depending on if the expansion is isothermal or adibatic) than the 2260 PCP with 65cc at 2000 psi.... If I can use the same percentage of that energy, I should, in theory, be able to get 20-21 shots at 20 FPE instead of only 16 shots at 20 FPE.... I sure as heck should be able to get 16 shots, the way I see it....
Bob
-
The reason why I had mentioned the possible leak is that I have two .177 CO2 models. Both have held pressure with CO2 over a period of time. One rifle was for indoor CO2 shooting and the other I am using to see if it is worth converting to bottled HPA. Anyways I had restricted the barrel port on one of the rifles to slow it down. I can feel pressure on my face when shooting the restricted rifle and not the other.
Adding a modification to these statements. I will have to pull the valve out to see if the seals were damaged when I install them. That may be the problem.
-
The reason why I had mentioned the possible leak is that I have two .177 CO2 models. Both have held pressure with CO2 over a period of time. One rifle was for indoor CO2 shooting and the other I am using to see if it is worth converting to bottled HPA. Anyways I had restricted the barrel port on one of the rifles to slow it down. I can feel pressure on my face when shooting the restricted rifle and not the other.
Adding a modification to these statements. I will have to pull the valve out to see if the seals were damaged when I install them. That may be the problem.
If it's blowing to your face it can only be from the barrel o-rings and probe o-ring. If it's blow back from the valve, you will feel it from the trigger housing. Barrel o-ring gets nicked from the step in the receiver when you insert it.
-
(http://img.photobucket.com/albums/v465/CWLONGSHOT/Graemlins/securedownload-1.gif)
-
Thanks Bentong will double check the barrel orings. You are probably 100 % correct. But the thought is both airguns have new barrel orings and the one with the restricted port insert has some blow back. Anyways something for me look into being that it is wasted air in my case wasted CO2. Or in my case could it be from the bolt probe oring. In any case it is probably not what is giving rsterne his perplexed readings. But figured it to be a long shot.
Must admit this boy meaning me has a lot to learn.
-
if the valve spring is too heavy
It makes sense that a lighter valve spring will extend the string as the reservoir pressure runs low.
-
It's a good idea to replace the bolt probe o-ring first thing. Of the ones I've seen they are all wore/smashed down and leak.
-
The trade off of a lighter valve spring being that eventually the hammer bounce from the last shot together with the force of the hammer spring will push the valve open and dump all the remaining air.
-
Thought I would throw in my findings and any better suggestions would be appreciated. I had changed all the orings with new ones. Then ran some grease between the receiver and barrel. When shot the grease had pushed out telling me that it was still leaking. Ended up wrapping the barrel groove six times with teflon tape (then trimmed the excess) put back the oring. Hoping this would tighten the tension on the oring. Still was some grease pushing out but not as much. Tried it again adding teflon tape to the outside of the oring (still with teflon in the oring groove) seems to solve the problem. So I tried the procedure the second time and dang it leak like there was no teflon but after 4 shots it tightened up. Anyways if some has a better solution I would like to know. I again posted it here because it may be related to rsternes findings. If not sorry to clutter up this thread.
Then again sendler2112 has a good thought also on the matter. JMO
-
The trade off of a lighter valve spring being that eventually the hammer bounce from the last shot together with the force of the hammer spring will push the valve open and dump all the remaining air.
I guess if you shoot down to 500 psi or less that might be a problem.... However, as you lighten the valve spring, you can back off on the hammer spring as well, in fact you HAVE to.... Having said that, the only time I tried a light hammer spring previously I had rapidfire hammer bounce at about 800 psi in a 9mm Disco Carbine, that emptied the reservoir and sounded like a machine gun.... On the other hand, I have successfully used NO valve spring as long as I kept the pressure high enough....
Bob
-
I thought maybe a lighter valve spring would make a difference to the usable pressure range, so I fitted one made from a 2240 hammer spring that was less than 1.2" long, so it had very little preload.... Basically, other than requiring about a turn less hammer spring preload, the gun shot exactly the same.... About the only thing I had left to try was a bstaley O-ring buffer.... Although intended for use with an adjustable length striker, I took a chance and dropped in three #113 - 70 D O-rings and because of the 0.050" I had machined off the steel backer block for the valve they were too short, so I added a "backer ring" under them against the steel block which was 0.050" thick to make up for what I had machined off.... I figured the chances of this being the correct thickness O-ring stack to work properly was slim to none, but at this point I was getting desperate.... I still had the gun set up as per the previous string with the 0.104" barrel port, and to my surprise I got a nice flat 17 shot string from 650-680 fps (about 18 FPE).... I tried one more turn hammer spring preload and the velocity moved up to 700, but right at the beginning of the string and then a dozen shots before it dropped 4%, so I was getting very close.... At this point I had two choices, either take a bit off the O-rings to increase the valve lift, or try going larger on the barrel port.... I decided to simply remove the barrel port restrictor, and boy was THAT the right decision.... I was rewarded with an 18 shot string starting at 698 fps, peaking at 718, and ending at 692.... a 20 FPE average, just what I wanted.... Here are the results....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/FD_PCPStrings_zps2609e4be.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/FD_PCPStrings_zps2609e4be.jpg.html)
This was a perfect scenario for the bstaley O-ring mod.... a gun that was overpowered with big ports and tons of flow, tuned down to use tiny sips of air very efficiently.... The total pressure drop was 475 psi, for a staggering efficiency of 1.57 FPE/CI.... I'm still limited to using about 500 psi for a 4% ES string, but with the number of shots, that is no longer an issue.... I can now set the gun up as a repeater using the 8-shot PRod magazine and get 2 full magazines at the 20 FPE level I wanted.... The best 20 shots are within just 20 fps from 1500 psi down to 1050....
So far I had not mounted a scope, so I really had no idea how accurate this gun was.... I borrowed a scope from another rifle, and was rewarded with it putting the 18.1 gr. JSB Heavies into a single 1/4" hole at my 20' inside range.... When a gun shoots like that, I know it's a keeper, and I don't even have to go looking for other pellets, because I know how great these work on Grouse at this power level.... One other thing I'd like to show you is the fill system I have.... I bought the parts from China on eBay for just $16.00, it will allow me to fill the gun from any paintball tank with a 1500 psi regulated output.... It consists of a fill station valve with 3000 psi gauge, an 8" braided hose, and a slide check which came c/w a female Foster fitting.... I bought the three parts separately and the vendor combined the shipping for $9.00.... and I received it in just a week....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/IMG_4142_zps07ad1269.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/IMG_4142_zps07ad1269.jpg.html)
Using a 48 CI 3000 psi tank will give me about 20 fills, and even a tiny 13 CI tank will fill it 6 times in the field.... wayyyyyyyyy more than you need for a days hunting.... Tethered to the big tank, I would have about 360 shots available, and over 100 from a 13 CI....
For those of you who might want to try the bstaley O-ring buffer in your FD-PCP, it's as simple as just pulling out the striker and dropping them in against the back of the steel valve backer block.... Use three #113 Buna O-rings of 70 Durometer, and see what you get.... It's too bad the gun doesn't have an adjustable nose on the striker, that would make tuning it a breeze.... but the basic idea is that if you need more power you need to thin up the O-ring stack a whisker (sand the front one down).... and if you need to slow it up more, add a thin shim between the front one and the steel block.... What you are doing is limiting the amount that the striker can open the valve.... which reduces the power and lengthens the shot string.... It works best when you are reducing the power a fair amount as in this case (going from 30 FPE down to 20) where I doubled the shot count.... If the stack is thinner, at some point it does nothing and you get full power.... At the other end of the scale, if you make the stack too thick, the striker won't hit the valve at all, and the gun won't fire.... The distance between those two extremes isn't a lot, probably less than the thickness of a single O-ring....
Oh!, I almost forgot.... While tuning the gun today I was adjusting the preload with the velocity adjuster, and suddenly the gun wouldn't cock.... I couldn't pull the bolt back far enough for the striker to catch the sear.... If I turned the preload a half turn in either direction it was fine, so I suspected that the shoulder on the adjusting screw was off-center just enough to catch on the back of the hole in the striker.... I pulled the velocity adjuster mount off the back of the gun, and sure enough, there was a shiny mark on the shoulder where it had been rubbing on the inside of the striker.... This would not be an issue if the adjuster was backed out further, but I needed to fix it, so I chucked the adjusting screw in the lathe and remove 0.010" (on the radius) so that it was the same OD as the spring and could no longer rub on the inside of the striker.... I reassembled the gun, and not only did it cure the problem and the gun now cocked fine no matter what the rotation of the velocity adjust screw.... but the trigger pull was MUCH improved.... I guess the striker, most of the time, was being pushed offcenter by the shoulder on the screw which caused it to bind on the sear.... So, I killed two birds with the one rock.... I was wondering why the trigger on this gun was so rough, and that was the reason, it was fighting against a binding striker....
Bob
-
rsterne you always amaze me how you figure things out. I know I had mentioned blow back earlier and thought I had fixed the problem by the grease test. But still felt the blow back and got me scratching my head. So you got me thinking even if I am running CO2 the bstaley mod may help me also. Thanks
-
Nice results with the oring tune. I couldn't get them to work in my Challenger. I tried 70D and 90D with a .080 port trying for 11fpe. The striker is in a good range, 3.5 turns extended. Plenty of adjustment to go either way. The hard orings were the worst. What I got was a normal rising string followed by a steadily descending velocity as the hammer got into the orings more and more. No flat area. Or I could reduce the spring preload with a lower fill pressure and get just a descending string with no initial rise. And I am not quite making it to my energy goal of 11.9 fpe. Now I am regulated at 1,600 psi so I will probably just take the orings out because the hammer energy is limited with the Challenger since it was originally designed for 5.7fpe. I have a situation where extending the striker increases the fpe initially by reaching down inside the orings more, up to a point, and then starts decreasing thefpe by reducing the hammer travel as a non oring tuned airgun would be. I also seem to be getting a lot of shot to shot deviation of almost 1%. Efficiency was decent at 1.65 fpe/ci, 9.91cc/fpe.
.
So I will probably switch back to the 2 times 70D orings and shave .010" off the spacer that is also in there to get the fpe up where I want it and keep the efficiency. But if I am still getting the shot to shot deviation then I will try it with no orings.
.
I know a lot of Marauder owners report exceptionally flat strings with the oring tune but it makes no sense to me how it can work out so well. What I am getting with my gun is what I would expect with any oring tune. A shot string which declines steadily with reservoir pressure once the hammer starts touching the orings. But I would expect exceptional efficiency due to the reduced ability of the hammer to burp through the orings after bouncing.
-
CO2 is a relatively constant pressure, so I can't imagine you would benefit from the bstaley mod.... You should be able to just use the velocity adjuster to optimize the striker hit to save gas.... Where it might come into play is if you want to dial back the power and go for a self-regulating CO2 setup that will deliver constant velocity over a wide temperature range.... However, that goes hand in hand with less power, AFAIK it won't work if you are struggling to get power from your CO2 setup....
I have a 1750 (2250 with an 18" long .177 barrel) and I can get 130 shots at 500 fps on a single 12 gr. cartridge, and the velocity is nearly constant from 35*F (right out of the fridge) up to 75*F, peaking at about 55-60*F.... The valve is self-regulating just like a PCP as the pressure changes with temperature.... However, the gun had to be detuned from about 650 fps to achieve that....
Bob
-
I too tried the bstaley mod on a Disco with little success.... It is better when detuning a gun that really breathes well.... ie first take a Disco, modify it to a 30 FPE gun, and then detune it back to 20 FPE with the O-ring buffer.... Then it can work well, and that is exactly what I'm doing here....
Bpb
-
CO2 is a relatively constant pressure, so I can't imagine you would benefit from the bstaley mod.... You should be able to just use the velocity adjuster to optimize the striker hit to save gas.... Where it might come into play is if you want to dial back the power and go for a self-regulating CO2 setup that will deliver constant velocity over a wide temperature range.... However, that goes hand in hand with less power, AFAIK it won't work if you are struggling to get power from your CO2 setup....
I have a 1750 (2250 with an 18" long .177 barrel) and I can get 130 shots at 500 fps on a single 12 gr. cartridge, and the velocity is nearly constant from 35*F (right out of the fridge) up to 75*F, peaking at about 55-60*F.... The valve is self-regulating just like a PCP as the pressure changes with temperature.... However, the gun had to be detuned from about 650 fps to achieve that....
Bob
I need to try that with my 1750. 130 shots with 12 gram is an ultimate plinker. I can't imagine what I'll get with 90gram AS, around 900+ shots maybe. Any tip on self regulating valve mod..
-
I'll start the fire, and get some sauce simmering...
Good job! He's gonna love the thing... if you can give it away now...lol.
-
I too tried the bstaley mod on a Disco with little success.... It is better when detuning a gun that really breathes well..
Breathes well and lots of extra hammer energy to smash through the orings so they become the by far dominant factor in the tune and the self regulating valve resistance becomes minimal in the total use of the hammer energy.
-
Try cutting a bunch off the 2240 hammer spring for a start, or fit a power adjuster that allows you to dial the preload down to virtually nothing.... If you can, lighten the striker to as little as 50% of it's original weight.... If you are aiming for a specific velocity (I had to stay under 500 to meet the Canadian laws) you may also need to fit a smaller transfer port.... Here are my shot strings at different temperatures....
(http://i378.photobucket.com/albums/oo221/rsterne/1750%20with%20DPH/WebShotStringsDPH9.jpg) (http://s378.photobucket.com/user/rsterne/media/1750%20with%20DPH/WebShotStringsDPH9.jpg.html)
The higher velocity, short curves on the left are stock.... the long, flat curves are in self-regulating mode.... Note the velocity is actually slightly lower at 75*F than at 46*F.... I also checked it at 35*F (right out of the fridge) and the velocity was about the same as at 75*F, but only about half the shots....
Bob
-
You might want to consider experimenting with heavier valve return springs rather than lighter. Peaky shot strings really just mean that dwell is increasing too much relative to the change in pressure per shot. A heavier spring will make dwell less influenced by pressure changes. After all, when you get right down to it, the buffer is just a very stiff return spring with a progressive spring rate.
A lighter hammer might help some too.
-
Bob,
I have decided that my FD-PCP is basically going to be a "14.3-grain PCP" while in .22 mode.
Reason being, I can access Crosman pellets locally, they provide plenty of energy for small game hunting, the reviews on most of their 14.3-grain pellets are really good and they are very affordable!
I will be testing the .22 Benjamin Discovery Extreme Hunter Sampler Pack in an effort to see which ones it favors the most. It is my understanding that the .22 Benjamin Discovery Extreme Hunter pellets are as good as the Boxed Crosman pellets? Not sure how true that is, regardless of that, the ratings for the .22 Benjamin Discovery Extreme Hunter pellets speak for themselves.:) I can get the Sampler Pack of them at Wal-Mart and a 500-count tin of the .22 Crosman pointed at the local Dick's Sporting Goods Store.
I also feel that the 14.3-grains will assist in a higher shot count.
In .177 mode, if it likes the CPUM 10.5-grain pellets, then they will be my go to pellets for that.
The testing that was done with the 32-grain Eun Jin pellets was more for fun than anything else, just to see what it could do after the tuning.
I have heard that once you find the pellet/s your Air-Gun likes the most, then it's sometimes best to just stick with them anyway.
Have a great week!:)
Respectfully,
Al.
-
LATEST SHOT-STRING USING A 1850-FILL and CPHP 14.3-grain PELLETS:
Bob, your thoughts?
(aside from the lower 1850-psi fill?)
1. 906-fps-
2. 912-fps-
3. 917-fps-
4. 927-fps-
5. 936-fps-
6. 936-fps-
7. 943-fps-
8. 934-fps-
9. 932-fps-
10. 924-fps-
11. 912-fps-
12. 905-fps-
High: 943-fps
High fpe: 28.24
Ended with roughly 1150-psi in the tube after this shot-string.
Respectfully,
Al.
-
Bob,
I have decided that my FD-PCP is basically going to be a "14.3-grain PCP" while in .22 mode.
Reason being, I can access Crosman pellets locally, they provide plenty of energy for small game hunting, the reviews on most of their 14.3-grain pellets are really good and they are very affordable!
I saw a video of the terminal performance of the new Crosman Destroyer pellets which are 14.3 gn. The .22 pointed hollow point folds out to turn into a .44" pointed pellet when it hits with enough energy..
.
.
http://www.youtube.com/watch?v=69Tfi3voZyc# (http://www.youtube.com/watch?v=69Tfi3voZyc#)
.
.
-
You might want to consider experimenting with heavier valve return springs rather than lighter. Peaky shot strings really just mean that dwell is increasing too much relative to the change in pressure per shot. A heavier spring will make dwell less influenced by pressure changes. After all, when you get right down to it, the buffer is just a very stiff return spring with a progressive spring rate.
A lighter hammer might help some too.
All excellent points.... the lighter hammer would be a good choice with this valve because of the small stem diameter relative to the throat size.... Shifting the hammer more towards energy and less momentum would make sense, which is what you get by going lighter.... However, I'm running out of spring preload (already below flush on the locknut), so adding more hammer travel would help.... A completely new hammer that was lighter and with an adjustable length striker would be an excellent thing to have, especially for tuning the gun with your buffer.... and maybe removing one O-ring, using a shorter protrusion on the striker to increase the hammer travel.... I'd have to look at other things (like the cocking pin hitting the slot and bolt) to make sure the travel can increase, though.... My gut feel is that it would work because of the buffer, maybe not without it....
Bob
-
Al, I already commented on that string in the other thread.... excellent results.... As to your statement about 14.3 gr pellets giving a higher shot count, I disagree, you usually get more shots as the pellet weight increases.... Also, you are pushing the 14.3 gr pretty fast, you are at the point where I would be looking at 15.9 gr. JSB Exacts, or 16.0 gr. Predators, if they are accurate in your barrel.... If you want the best in long range accuracy, it's pretty hard to beat the JSB Exact Series in one weight or the other.... The 18.1 gr. Heavy is my all time favourite pellet in .22 cal....
Bob
-
Today I modified the receiver to accept the 8-shot .22 cal PRod magazines.... This was NOT my idea, I borrowed it from stalwart on the GTA who originally used a 10-shot .22 cal MRod magazine.... The basic idea is to machine a notch big enough for the PRod magazine in the receiver.... It looks like this....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/IMG_4145_zps85890bf5.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/IMG_4145_zps85890bf5.jpg.html)
You can see the back of the barrel which has been machined to 7/16" OD and protrudes 1/16" into the notch, providing a stub for the magazine to clip onto.... I used a 5/8" end mill and the notch is 1/8" deeper than the bottom of the barrel stub.... I removed a small amount of the front of the existing breech opening, and also faced a bit off the face of the bolt to get enough room for the magazine.... Here are the modified barrel and bolt....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/IMG_4148_zps5178b740.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/IMG_4148_zps5178b740.jpg.html)
I cut the stock bolt nose off 0.40" from the (new) bolt face, drilled and tapped it 8-32, took a piece of 1/4" drill rod 3/4" long and did the same with it and used a 1/2" long piece of an 8-32 screw as a stud to attach the new front of the bolt to the old stub using loctite.... I then turned the shaft of the bolt down to 7/32", and the probe section down to 3/32" and adjusted the lengths so that the shoulder is flush with the back of the barrel port and the probe pushes the pellet just past the port....
The mods to the barrel were tricky.... I used the old front O-ring groove for the rear O-ring and cut the barrel off about 1/8" behind that, losing about an inch of length.... The 1/2" OD portion of the barrel is a lousy fit in the receiver, so when I moved the shoulder over, I made it a better fit.... The locatons of the O-rings, barrel port (on the bottom so not visible in the photo) and the set-screw hole are all critical, as is the 7/16" shoulder.... I didn't add a groove for the third (forward) O-ring I don't see any reason for it.... Also what you can't see, there is an internal O-ring groove inside the barrel in the space between the external O-ring and the back.... That O-ring is a #009 and fits nicely on the 7/32" bolt nose to seal it.... I had to rechamber the barrel of course.... Here is the breech with the magazine in place....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/IMG_4146_zpsc7cad4b3.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/IMG_4146_zpsc7cad4b3.jpg.html)
It took a ton of measuring, thinking, drawing sketches, and careful fitting to accomplish this job, and my thanks to stalwart for all his help.... If you want to get your FD-PCP or XS-60C converted as a repeater, please contact him on the GTA Forum....
Bob
-
As always - thanks for sharing this build with us! I love seeing how a plan comes together.
-
Bob,
Are you suggesting that Stalwart is offering this mod as a service? At a price of course.
-
Bob,
Are you suggesting that Stalwart is offering this mod as a service? At a price of course.
Here's the link to the project, Bill.
http://www.gatewaytoairguns.org/GTA/index.php?topic=59114.0 (http://www.gatewaytoairguns.org/GTA/index.php?topic=59114.0)
-
Al, I already commented on that string in the other thread.... excellent results.... As to your statement about 14.3 gr pellets giving a higher shot count, I disagree, you usually get more shots as the pellet weight increases.... Also, you are pushing the 14.3 gr pretty fast, you are at the point where I would be looking at 15.9 gr. JSB Exacts, or 16.0 gr. Predators, if they are accurate in your barrel.... If you want the best in long range accuracy, it's pretty hard to beat the JSB Exact Series in one weight or the other.... The 18.1 gr. Heavy is my all time favourite pellet in .22 cal....
Bob
Bob,
I will most definitely look into the 15.9-grain JSB Exacts!
Just received my first tin of 18.1-grain JSB pellets and must say that I am very impressed by them.
Hopefully, you can pick up a pretty good deal on the 15.9-grain JSB Exact pellets; long range accuracy is what I after.
Regards,
Al.
-
Today I modified the receiver to accept the 8-shot .22 cal PRod magazines.... This was NOT my idea, I borrowed it from stalwart on the GTA who originally used a 10-shot .22 cal MRod magazine.... The basic idea is to machine a notch big enough for the PRod magazine in the receiver.... It looks like this....
Bob, why did you go with the PRod magazine instead of the Mrod? Convenience or issue with fit? Also, I know that these are not interchangeable-- can you tell me why? I've been searching for an answer on this for a while and haven't found anything.
-
Bob, it's beautiful. Pure and simple.
Guys, if you ever get a chance to collaborate with Bob... take it. I learned a bunch, and the guy is kinda fun to hang with!
I am doing a short first run on these (in 10 shot), to nail down some cost numbers and techniques. I have parts left for 2 more guns or conversions, in this run. PM if interested. Lead time on the next run is TBD.
The pistol mag is more compact, takes longer pellets, and a gun modded for them will take Lloyd's .30 cal (7 shot) mags. I'm going that route in a long term project I can't wait to start. Neither has issues with fit, but, neither can just be slapped in. They each have their own reasons for careful work, and both are good choices for their own reasons. Here's a pic of the Mrod setup... you can see that the pistol mags tuck in very nicely, and will leave room for a smaller scope, set low.
-
Well I got the rifle back together today, and it works beautifully.... I get 20 shots from 1500 down to 1000 psi within 30 fps (4%), 692-720-692, which averages 705 fps (20 FPE) so that works out to 1.66 FPE/CI, which is stellar efficiency at that power level.... The bstaley O-ring buffer really works well to detune this gun for moderate power and lots of shots.... It stuck all 20 shots in the same 3/8" OD hole (at 20') while running the string through the Chrony, so the accuracy will be there I'm sure....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/IMG_4192_zps95605b18.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/IMG_4192_zps95605b18.jpg.html)
With a Leapers 3-9 x 32AO scope in medium rings the tube easily clears the PRod magazine, although if the turret sticks down very far below the tube on your scope, it may not fit unless, like on mine, it is either in front of or behind the magazine.... The gun as shown above weighs 6 lb. 13 oz., so it's under 6 lbs. without scope, and with the 1" shorter barrel the gun is under 39" long.... I would say that if my son can shoot, the Grouse are in for a really bad time this fall....
Bob
-
Sorry, stalwart, but the .25 cal (and Lloyd's .30 cal) mags are 0.050" longer yet again than the PRod mags (which AFAIK are only available in .22 cal).... All the MRod magazines are the same height, however, but the PRod (being 8-shot instead of 10) is lower (more scope clearance) and requires a shallower cutout below the barrel.... One benefit of the PRod mag is that it will take Predators.... Yes, it was a lot of fun picking your brain on this project, I really do appreciate the help.... Any of you guys that want a repeater, I'm sure it will be worth the cost of the conversion....
Bob
-
Very nice. You guys amaze me with this stuff. I wish I had an unlimited budget, I would take two of everything you guys do. However, if I don't want to grow old and die a lonely man, I need to throttle my cravings.
-
Those are such nice setups. I'm feeling jealous. I so bad want to be a machinest.
-
If only this was possible with basic tools...
-
If only this was possible with basic tools...
Agreed, this would be a tough task with my flat file and Harbor Freight screw driver set.
-
If only this was possible with basic tools...
Agreed, this would be a tough task with my flat file and Harbor Freight screw driver set.
I was talking to Betty Lou about these guys and she said she wouldn't want their electric bill.
-
She's right.
If more people understood how much of a shop rate a competent owner actually takes home... there would be less people wishing they had a shop.
I like Betty Lou, and you can tell her I said so. Always liked smart girls. :)
-
Yeah, I kinda like her too. Her list of qualities is endless. I'm a lucky guy.
Thanks
-
Is this XS60C PCP based on the first generation rifle and using an aftermarket fix for the leak at the valve? What was the fix? I can't find the other thread where it was discussed.
-
Is this XS60C PCP based on the first generation rifle and using an aftermarket fix for the leak at the valve? What was the fix? I can't find the other thread where it was discussed.
Add an 113 oring in the rear end of the valve so there are two side by side. Yes it is the first gen rifle. I think the second gen has a different designed valve. All the PCP rifles are all fixed for leaks by Mike. The CO2 first gen rifles can be bought fixed for $70 and unfixed for leaks at $50.
To change the subject my hats off to rsterne and stalwart. Glad they are members of the GTA.
-
Thanks, Paul.
It's an honor to be in present company.
-
Since this seems to be one of the best XS60c threads, hopefully my question will fit...
I'm working on modding my v1xs60c to use a 13ci regulated hpa tank and I really want the fitting to exit straight out from the pressure tube. I see most of these are made of brass, and a lot of people modding them continue using brass, but brass is so expensive I wanted to use something else. Guessing at the alloy of the brass (c360) gives about the same tensile strength as 6061 aluminum at around 40,000 psi. The aluminum is also easier to machine. Does this sound like a safe material to use for this purpose.
As a side note, looking at the Marauder pistol, it has an aluminum endcap on the pressure tube but hard to tell the alloy from looking at it.
-
If you try and align the regulator threads with the end of the tube the tank will hit the barrel.... You need a dropped style tank mounting block like used on the QB79, which should fit OK.... You can also purchase them from JDS Airman, and they have the mounting screws further from the end of the tube which is stronger than the QB block.... However, they don't have a pin to depress the pin valve in the end of the regulator so you have to remove it and you can't take off the tank with ANY pressure in it.... The QB and JDS mounting blocks are both aluminum.... Make SURE the regulator is fitted with a 1.8K burst disc on the output side to protect the gun in the event of a regulator failure.... This will limit you to 1500 psi for the setpoint.... I recommend using high tensile screws in the block, the ones that come with a QB79 are VERY soft....
Bob
-
I'm going to remote the tank with some stainless 8500 psi tubing and stainless 5500 psi fittings, should give me enough overhead to make things safe. Not the cheapest materials, but should produce a good durable assembly. I'm thinking of running the regulated pressure somewhere in the 1200 to 1500 psi range so the 1800 burst disk is right on track. Had to go with higher rated tubing because the fittings called for the thicker wall.
How deep should I thread the 1/8 npt hole in the rifle tube endcap? And since you do a lot of machining, can I get away with just a cheap carbon steel tap? I only plan on making a couple of these end caps so I don't want to spend 6 times the price on a good tap to only need it for about two holes.
-
thread quality is EVERYTHING especially when dealing with high pressure...
nothing is worse than a crappy tap and I do mean NOTHING...
the flaming rest room stomach flu (yeah THAT one) is better than a crappy tap..
you need REAL threads...a good quality 1/8 npt ought to be less than $15
-
Posting to bookmark, Great info.
-
Bob,
Is the probe and valve supposed to slide out after you unscrew everything? I tore mine down to every individual piece, except I can't get the probe, valve and hammer out of the action/breech block. Hopefully my question is clear.
-
The valve and the steel block behind it slide out the front of the receiver where the tube screws in.... You have to loosen the front of the valve a half-turn to undo the pressure on the o-ring first....
The hammer and bolt slide out the back.... There is a pin in the hammer that engages in the machined recess in the bottom of the bolt, and you have to remove that pin to be able to slide the two parts out the back.... There is likely a setscrew installed over the pin to lock it in.... Remove the setscrew through the slot in the bottom in front of where the sear is, and then using a slotted screwdriver, remove the pin also.... The bolt and hammer will then slide out the back.... You have to have removed the bolt handle and the rear adjuster block first, of course....
Bob
-
Thanks for such a quick reply. I finally got the valve, hammer and probe out. Thanks again.
-
When I twisted open the valve housing, spring, valve needle and black shim fell out. What is the arragement order again? Black shim, spring and needle or spring, needle and the shim? Thanks in advance.
-
Shim, spring , Piercing pin. The same order as a C160-180 valve.
-
Thanks a lot.
-
One other thing I'd like to show you is the fill system I have.... I bought the parts from China on eBay for just $16.00, it will allow me to fill the gun from any paintball tank with a 1500 psi regulated output.... It consists of a fill station valve with 3000 psi gauge, an 8" braided hose, and a slide check which came c/w a female Foster fitting.... I bought the three parts separately and the vendor combined the shipping for $9.00.... and I received it in just a week....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/IMG_4142_zps07ad1269.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/IMG_4142_zps07ad1269.jpg.html)
Is there a bleed valve on that setup? Is it necessary at those pressures?
-
One other thing I'd like to show you is the fill system I have.... I bought the parts from China on eBay for just $16.00, it will allow me to fill the gun from any paintball tank with a 1500 psi regulated output.... It consists of a fill station valve with 3000 psi gauge, an 8" braided hose, and a slide check which came c/w a female Foster fitting.... I bought the three parts separately and the vendor combined the shipping for $9.00.... and I received it in just a week....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/IMG_4142_zps07ad1269.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/IMG_4142_zps07ad1269.jpg.html)
Is there a bleed valve on that setup? Is it necessary at those pressures?
If there really is a slide check you don't need one. That large gold ring just before the female foster should be the slide check. The collar should slide to open and close the valve in the line. When closed, it vents the space between it and the foster fitting. It allows for less wasted air compared to venting the whole line. Just be sure not to slide it to open without it connected to a gun or it will vent the rest of the line. You don't want the tank valve turned on of that happens either.
-
Lots of great lore and sharing here - being a retired engineer stuck on my back for a month or two now, and fairly new to the airgun hobby/addiction; this is such a good crash course, I've started to lust after my first pcp.
If someone wouldn't mind a simple question, what are the exact O.D. (14mm?) and length of the XS60c PCP .22 barrel? I'm thinking I want a 24" match barrel, since it has to be pulled for the repeater mod anyway. If I use a tank I'd rather use a turnaround block and maybe a longer plenum (why not make an .083" 4130 tube?) and use the slightly longer (22ci)regulated tank? Not knowing dimensions I'm not sure if that's feasible. Maybe someone wouldn't mind shooting a pic of one of these guns against a yardstick or something?
[P.S. Never mind the yardstick.
As of this week I am not only the excited owner of the "fakie GEN I" and pump, but the proud father of my first low pressure valve lock &/or fill block leak.
The fill block hisses when I pump and no pressure registers.
I'm about to embark -As Safely As Possible- today, on the dreaded 'first degas/teardown'- unfortunately, the first of many. Until next month's paycheck I can't get a gauge and bottle setup, so for a couple of weeks, I won't know how to avoid shooting it down that far again except by trial and PITA error. Oh well, I can spend it timing and improving my teardowns like a PB gun nut, and welding up a wrench to use on the valve I'll mod to be slotless a la "scot laughlin's" pic -bottom of the page- at: http://www.network54.com/Forum/79537/thread/1390869883/Flying+Dragon+PCP+Valve+Fix (http://www.network54.com/Forum/79537/thread/1390869883/Flying+Dragon+PCP+Valve+Fix)
-which won't be that neat, as I don't have a mill - just a grinder and my old eyes.]
LOVING this gun, and the information provided by the GTA crowd!
Thanks-
Rod
-
Lots of great lore and sharing here - being a retired engineer stuck on my back for a month or two now, and fairly new to the airgun hobby/addiction; this is such a good crash course, I've started to lust after my first pcp.
If someone wouldn't mind a simple question, what are the exact O.D. (14mm?) and length of the XS60c PCP .22 barrel? I'm thinking I want a 24" match barrel, since it has to be pulled for the repeater mod anyway. If I use a tank I'd rather use a turnaround block and maybe a longer plenum (why not make an .083" 4130 tube?) and use the slightly longer (22ci)regulated tank? Not knowing dimensions I'm not sure if that's feasible. Maybe someone wouldn't mind shooting a pic of one of these guns against a yardstick or something?
Thanks-
Rod
Rod;
The 3 people you want to talk to are Mike Mellick, RSterne and Stalwart. Not in any particular order.
Enjoy
-
The barrel on an FD-PCP is 14.5 mm diameter (15 will clear the tube no problem) but the part inserted into the breech is about 1/2" (and a poor fit).... It is about 21" long.... If you get an LW 15mm barrel (23.8" LOA) you can turn it to fit the breech.... I developed the reverse tank blocks, and despite having tried to give away the design a couple of time, no enterprising machinist is producing them.... For a .22 cal shooting, say 35-40 FPE you can get a large enough plenum with a 13 CI tank.... If the back of the tank was at the front of the receiver, the plenums would be about 43 cc with a 13 CI tank, 57 cc with a 17 CI, and 80cc with a 22CI.... Unless you want the larger tank for a ton of shots, I would use a 13 CI for .177 or 22 cal, a 17 CI for .25 cal, and a 22 CI tank for anything bigger.... A 4130 CrMoly tube that is 7/8" OD x 0065" wall is plenty for 3000 psi working pressure, no need to go thicker.... although it would increase the strength of the threaded area (if you still use the threads)....
Bob
-
Hey Bob,
Great thread; these are the kind of posts "Tinkerers" like me need to understand basic PCP mechanics.
I will be tuning my BAM B-50 pretty soon and need to fill my brain with your & Motorheads tuning/regulator knowledge ;).
Kirk
-
The barrel on an FD-PCP is 14.5 mm diameter (15 will clear the tube no problem) but the part inserted into the breech is about 1/2" (and a poor fit).... It is about 21" long.... If you get an LW 15mm barrel (23.8" LOA) you can turn it to fit the breech.... I developed the reverse tank blocks, and despite having tried to give away the design a couple of time, no enterprising machinist is producing them.... For a .22 cal shooting, say 35-40 FPE you can get a large enough plenum with a 13 CI tank.... If the back of the tank was at the front of the receiver, the plenums would be about 43 cc with a 13 CI tank, 57 cc with a 17 CI, and 80cc with a 22CI.... Unless you want the larger tank for a ton of shots, I would use a 13 CI for .177 or 22 cal, a 17 CI for .25 cal, and a 22 CI tank for anything bigger.... A 4130 CrMoly tube that is 7/8" OD x 0065" wall is plenty for 3000 psi working pressure, no need to go thicker.... although it would increase the strength of the threaded area (if you still use the threads)....
Bob
Thanks, Bob! I actually was considering both the longer barrel for even more power, trying to use all the flow I can get out of the FDPCP (and max. FPE by using huge pellets,) and adding a few more shots by a bigger tank, as the barrel length would allow. The strength and safety of attachments on both ends of the tube, are what I was considering in adding wall thickness up to the next size (.083") The threaded area back at the action would be stronger as well as the screw holes with proximity to the fill block end.
It appears, from what I'm reading, that I'd have the absolute minimum number of shots this gun can provide, when going for absolute max FPE. But I would also want to have Eric make it a repeater, so adding a couple of shots per fill makes sense there.
As I've mentioned, I like a gun to be heavy, and especially now that offhand shooting (and hiking) have receded far into the past, at my age. I just want the distance and accuracy off whatever rest or 'bench' I have for comfort. It's more about protecting the garden at a distance, out the window, from my couch or armchair (or my garage workshop.) Like anyone, I enjoy and need a good plink now & then, to stay accurate if nothing else, but even that's more fun if I can blow stuff apart with authority. I'd also like to be able to use the local pb range (it's free!) without too much embarrassment...
(Now to find a cheap waterjet guy to make me some 'jumping jacks'... Even the sale price of $25 is too much for a target when tin cans are free.. I just finished the pattern to make my own. I figure 3/32" 4130 sheet. Then I'll need a powdercoater - if I can wait that long ;) Wife is picking up some 2" Shoot-n-C's for it (and some Soft Scrub) 'Idle hands,' for this shut-in, are dangerous. ;)
The .22 FDPCP 'fakie Gen 1' & pump arrive MONDAY!
Fingers crossed for a non-leaker ... A PCP virgin, I'm limited to the pump for now and it looks a lot harder to diagnose without a tank.
MORE POWER MODS, please!
Even 8 shots a fill is fine with me, if I can get closer to 50 FPE than 20. I can't wait to see what the Magical Mr. Mike has concocted for a compromise between the (possibly) leaky Gen 1 (which I would have preferred, especially for $65 less...) and the plastic Gen II...which I hope isn't less easily power modded. Anticipation....
-
If it leaks you can fix it.
If this idiot can, so can you. If you could disassemble the gen 2 and get some photos that would be great. I can't be the only one wondering exactly what changed inside.
-
If it leaks you can fix it.
If this idiot can, so can you. If you could disassemble the gen 2 and get some photos that would be great. I can't be the only one wondering exactly what changed inside.
I promise I'll get the requested pix while it's open today/this week.
I might as well since there's probably a lot of polishing (and definitely measuring, etc.) to do,
while waiting for Aug1 and bottle conversion funds.. it occurs to me this move to the DarkSide is not only a self-indulgent consolation (for this month+ of dysfunctional pain & suffering waiting for back surgery,) but also a birthday gift (next Wed.)
TBTG payday comes early this month - only a week 'til Rev2.0 (HPA a/k/a "The Bottle") can begin!
Still can't decide on an ASA though.
My thoughts run to a more minimal looking cylindrical black one-
like the JDS or the Chinese eBay one, but I may decide it's too hard to screw.
I'd also like to get a checkvalved Foster male to screw in place of the reg (or the ASA/nipple,)
so I could fairly easily choose to drop the tank and go PCP on rare occasion.
UPDATE: This morning, I was able to pump it up after cocking it
(which I refused to do before I got that last pellet out of it, from when it stopped shooting) and it took the air - 53 pumps to get up to 100bar.
- BTW is that too many? Is the valve in the pump working right?
Upstroke seems easier than I had expected...
Guess I'll spend the first half of today continuing to zero the scope, at 40yds this time.
Maybe I'll stop at 6 shots this time and see if it locks or leaks.
THEN I'll clean the barrel and tear down completely,
maybe tomorrow shoot some pics and clean up/polish etc.
I swore I wouldn't start modding until it screwed up and forced me to tear it down...
Then there's the "PHONY" (DIY CHRONY) I built, yet to be tested and its software calibrated..
I need to build a bench for that.
Rod
-
I posted this pic once (as I had promised to do when I got the GEN II apart)
with a fairly long post in explanation of the shot curve etc. (which I didn't save...)
and for some reason I'm left only to guess, it disappeared.
I never got a notification or an error message.
One more try (just to see what the problem is.)
[Update: It appears the site can't handle a 1.21MB pic.
Unfortunately I haven't had this experience before on a hardware-oriented site
and am AFAIK incapable of taking low res pics.
I never really found them useful anyway, even when I had a cheaper cam.]
If it takes, and anyone has questions about my GEN II, or the shot count (this is a .22, ordered power tuned, and requested and discussed "with no plastic." The barrel band, behind-valve spacer ("plug") and trigger group block, are plastic. It got ten pretty powerful (@ least accurate, more accurate than I am certainly,) shots pumped to 1600psi, JSB 18.13gr Exact Jumbos, before it started to drop at 41yards. Shot #11 was 1/2" low, #12 1" low, and #13 was 2" low The charge went for 21 "shots" - the last few dry fired, before running out of air. It was completely empty on a cautiously redundant de-gas check during teardown.) I think it might shoot the similar weight Kodiaks well also (as does the Benji) but shows some promise with the 25gr+ JSB "Monsters."All the JSB's seem to chamber comfortably on loading. The 32gr. Eun Jins drop badly at that distance though, and they will be my power tuning goal for now. The H&N "Rabbit MagnumII's" (~25gr.) are VERY tight loading and not accurate at all so far. From my recent experience with the Benji starting to prefer the Kodiaks over the JSB's, after over a year, I expect these things to change too. I want to feed it a little more air (with a 22ci bottle at 1600psi and some safety and valve mods) and see what happens. I can almost sense it wanting to wake up and be a little less reserved. I think Eric can help.
No chrony this time, but I've built one that I will try after cleaning, polishing and modding the gun a little. And after building a bench to hold the gun and 1" tube DIY "chrony" in registration. If it works and is usable after tweaking the sw, I'll build one with far more LED's and phototransistors (they're cheap, this one has two and six respectively) in a 6" tube. That should take about 24 semiconductors, and they're only about $1 each. The tube costs more than that- and the sw is free. It's built for audio (mics) but it doesn't care if it gets photocell input instead. A pulse is a pulse, and light is faster=more accurate.
When I get time I'll consider finding a drop site for pics, and try to notice if there's a favored one here.
I didn't realize this limitation existed when I made that promise, sorry again.
Rod
-
I'm very much wanting one of these... but I don't have a clue about much of what you guys are saying as far as how to modify. I see why much of what you were doing but don't understand how!
-
I have had a couple of questions about the fill setup I built with Chinese parts I purchased on eBay.... I made this setup, which I posted earlier in the thread....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/IMG_4142_zps07ad1269.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/IMG_4142_zps07ad1269.jpg.html)
I had a problem with the slide check valve.... It kept blowing O-rings.... The rest was fine, but I had to remove the slide check and fabricate a bleed valve, which I did as follows....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/IMG_4338800x401_zps50031afc.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/IMG_4338800x401_zps50031afc.jpg.html)
I removed the gauge on the side of the ASA valve and installed a steel 1/8" to 1/4" adapter which I drilled and tapped to 3/8"-24 NF for a short bolt.... I made a Teflon (you could use Delrin) insert to seal against the bottom of the drilled hole.... When you hand tighten the bolt it seals for filling, and when you loosen it, it bleeds the air out of the hose through the small cross-hole just visible on the bottom of the bleed fitting (on the smooth portion between the threads and the hex).... This worked perfectly.... I understand that Mac1 Airguns sells a US made slide-check that doesn't have O-ring problems, so that would work also....
Bob
-
Does anyone know if the B-51 stock will fit the XS60?
-
I know what OTC means - that was my first wish on the FD as well.
Next was the QB/AR thumbhole stock but that seems unavailable at the moment.
I've settled on the AR2078A stock, and yes, they all will take a lot of work from the user, but who has $500 for a STOCK? If I even had $500 to spend I would've bought a .25cal Mrod or Hatsan or something.
It's hard enough affording minimum air supply stuff on a fixed (SS) income.
But new back problems & surgery will not allow pumping my Benji any more, maybe forever. It was getting too hard, for too little shooting, at my age. I just tried it after a few months being idle, and now its power is completely gone anyway. I watched the pellet drop FEET before it hit the ground- at 40 yards on 8 pumps. Some day it will take a cross country trip to Tim (extended billet steroid) if he's still worklng.
-
Does anyone know if the B-51 stock will fit the XS60?
It will not.
Even with a LOT of work the Bam tube channel is MUCH larger than the FDpcp
John
John,
Is the only problem that the tube channel is too large?
Does Boyd's Blasters make a stock that will fit?