2400kt, Bottled, Regulated

[aPpYe]

Hi All,

It seems that I DO have free access to a lathe and a milling machine through work!  Woo hoo!  The mill works both manually and is computer programmable, I guess that means CNC?  The lathe is manual only.  Of course, I never even took machine shop in high school.  I have zero skills in this area.  I uh, did give myself a concussion once by running a wood lathe at max speed on a fresh 6x6.  High school was fun!

Anyway, this being the case, and now that I have the money cobbled together for this, I figure I might save a little by bottling and ninja regulating a CCS 2400kt with a 24” barrel, rather than buying a Disco and doing the same.  I have thought long and hard about going with the QB line, but at nearly 7 pounds, they might be uncomortably heavy after carrying around for a while.  I have noticed it seems there is a general consensus in the community that the QB barrels tend to be of higher quality, so I recognize that I may be looking at fitting an aftermarket barrel if I am unhappy with the accuracy.

I figure it is mostly going to be used for plinking and some target shooting, NOT scoped and with peep sights.   I may hunt some with it, but I figure I have my steroid silver streak a couple of powder burners for that.  Having a lot of power is not really what I am after.  That being said, higher velocities (sub transsonic, of course!) are a must, as I want to reach out as far as possible with minimal sight adjustment.  I would like to shoot accurately at 50 yards if I can.  I figure I should go with .177, as it will get me higher shot counts (I am even considering the 22ci ninja regulated bottle I see at MAC1!) and it will be easier to get to the 850-900fps range with 8-10 grain pellets.  Please correct me if I am wrong with these assumptions, I know that the the larger calibers tend to be more “efficient” psi/fpe wise.

I see a lot of people going with the 13/3000 ninja regulated setup at various pressures.  I have seen it preached many times that I want to have two “burst discs,” typically with 3000psi at the bottle and 1800psi at the regulated side, to keep things safe.  I would like to keep the pressure as low as possible to keep shot counts up anyway.  Are the ninja regs the only ones with this dual burst disc feature?  Any thoughts on  safe pressures with these guns?  At what psi would I need to start adding pins to the valve?   I don't want any bombs going off.

What can I expect velocity-wise with a 2400kt on say, 850psi out of the box?  What about something like 1200psi?  I notice that the tubes are pretty short.  Is 875fps with an 8 grain pellet even feasible with this setup?  What about 10 grain or higher?  Am I going to have to start looking at longer tubes?  Should I be looking at aftermarket valves and whatnot, or can can this novice machinist expect to be able to succussfully modify stock components with the aforementioned limited skillset?  I am planning on learning the basics with these machines on throwaway pieces of metal and whatnot.

I have been researching these Crosmans for a few days now, and noticed the huge aftermarket for them.  I see aftermarket valves, tubes, triggers, RVA's, just about everything.  It seems, like the ruger 10/22, I can pretty much build these crosman 2xxx guns without ANY Crosman parts!

I am extremely close to finally making a decision on this!

[EdinGa]

I can't speak for .177 but I'm hitting 620fps with 14.3 gr .22 pellets in a 2250 14 inch barrel on 850 psi. It has a lightened  hammer, and a 1322 spring.

[rsterne]

IIRC, the tube on a 2400 KT is the same length as a 2250 tube, is it not?.... Making that assumption, and using a tank block similar to a QB79, you would have a plenum volume of about 24 cc (without a gauge block, or 17cc with one).... That is plenty for up to 24 FPE (17 FPE) with good efficiency, so your setpoint pressure will not have to be increased to look after plenum size.... 850 psi of air will give you more velocity than you get at room temperature with CO2....

With 1200 psi, you will get about the same velocity as a stock Disco at the bottom end of the shot string.... That means about 800 fps with 14.3 gr. pellets in .22 cal with stock porting.... In .177 cal, getting 850 fps with 8.4 gr. pellets should be equally available, maybe a bit more.... I had one set up for FT at 20 FPE, which is 10.3 gr. pellets at 900+ fps, but that took 1500 psi (which you can still do while using a 1.8K burst disc).... So, you can do pretty much everything you have in mind by using 1200 psi, but if you want to push the 10 gr. that fast, you may need to go to 1400-1500 psi.... Once fully sorted, my .177 FT gun got over 100 shots at 19+ FPE from a 13 CI Ninja tank at 1500 psi.... A bigger tank would give you proportionately more shots, of course....

One thing I can't stress enough.... MAKE SURE YOU ATTACH THE VALVE WITH THREE SCREWS.... I would use a Disco valve and screws for what you want to do.... and make sure you drill the tube accurately so that the two side screws are taking their share of the load.... If you want even better screws, you can use the valve screws from a PRod, but make sure you drill the holes in your tube to fit the heads (they have smaller heads than the Disco screws).... However, the bottom hole valve hole in the tube is already the correct size for the PRod screws....

Bob

[aPpYe]

Wow Bob,  those numbers are more than what I was expecting!  I was thinking I was gonna hear about how I needed to do all kinds of modifications to achieve what I am after!

From what I understand the tubes are of identical dimensions

Your recommendation of a disco valve and screws are based on a 1200psi reg?  Is 1200psi what you recommend?  In order to achieve 850+ fps with 8.4 grain pellets, how low do you think I can go with the air pressure, maybe with some porting and/or valve work, or other machining?  14+ FPE would be perfect with 8.4 gr pellets, but I surely wouldn't mind getting some 10+ gr pellets up to those velocities as well!

Perhaps there is a walkthrough on getting the extra screws in there?  I would think it easier to drill the holes with the valve in the tube, so they are guaranteed to match perfectly.  I need to research this.  I also hope not to mar the lazer etching that Crosman puts there, but I have to I have to.  Maybe I can add a bunch of spaces before my name, “aPpYe” at the CCS, so as to avoid this.  Where, in the CCS screenshot below, would the screws go, exactly?

Rsterne:  The Almighty Zeus of modern airgunning ...  Basically, I plan on doing exactly what you tell me to do!

[rsterne]

I would start with 1200 psi and adjust up or down if you need to, it is only shims required to do that.... and I'm betting you can get what you want at that pressure.... You might hit 14 FPE with less than 1200 psi, but driving 10+ gr. pellets in the mid 800s is about 17 FPE, and I think you will need at least 1200 psi to do that in .177 cal.... OK, maybe you might do it with a Ninja SHP regulator, which is 1100 psi, so if you can find one of those, go for it.... If you can't, get Tim @ Mac1 to build you a 1200 psi setup....

You are going to have to learn to drill accurately to accomplish your goal.... You will need to shorten the front of the 2400 tube to behind the threads, so that you are working with the full thickness tube wall, and then drill that for the two screw holes to install a QB79 style tank block.... You will need to get a Disco valve, which will fit inside the 2400 tube, but it is drilled and tapped for three 8-32 screws, instead of the single 6-40 screw that retains the CO2 valve now.... Do NOT try and do this conversion using a single screw holding the valve, they can come out the back.... At 1200 psi, there is over 500 lbs. pressing on the valve.... If you use the PRod valve screws the hole in the bottom of your tube is the correct size, but you will need to drill two additional holes, one each side, accurately lined up with the holes in the Disco valve, so that all three screws share the load on the valve.... If you don't feel confident that you can drill these holes accurately, then find someone who can....

Bob

[aPpYe]

Awesome!  I will be ordering my CCS gun before the weekend is up!!!  Exciting stuff!  I will have to look into the whole drilling thing before I decide whether or not I can do it myself ... I do have a drill press... I guess it is just measuring things and putting the hole in the right spot.

I won't have to do any porting or other machining to get the performance I desire?

I am not sure I follow about the SHP regulators though.  Why would they equal 1200psi performance with just 1100psi?  Or are the non-SHP regulators not available in 1100psi?  This one is throwning me for a little bit of a loop I must admit.  For some reason I thought all the ninja regs were SHP.

Also, could you tell me where exactly the screw holes go for the disco valve, in relation to the laser etched  engraving?  I would like to try and avoid drilling through the letters if I can.

[rsterne]

You likely won't have to do any porting, particularly in .177 cal.... In fact, I wouldn't start hogging things out, you just might lose, not gain, in .177 cal....

The SHP regulators are ONLY available in 1100 psi.... The standard paintball regulators are 850 psi, and use a coil spring, not a Belleville stack.... The Ninja regs. you get from Tim @ Mac1 are available in 1000, 1200, and 1400 psi.... Either 1100 or 1200 should work for you, and you can fine tune them with shims if necessary....

I have never had a 2400 tube, so have no idea where the Laser etching is, and it may vary tube to tube, anyway.... The holes for the valve are on both sides, exactly lined up with the lower screw hole, and at 90* to it on each side.... You will see what I mean when you get a Disco valve in your hand....

Bob

[aPpYe]

I have to admit I am almost disappointed in how easy this project will be.   I was looking forward to learning some machining skills!  So I guess here come the inevitable questions.  Drumroll please...  What further modifications would be required to get those 14.3 gr .22's to the high 800's?  How about heavier pellets?  I might just want to cut some metal!

That said, I am admittedly somewhat intimidated by the idea of getting the valve pins in exactly the right place.  I did not realize that the holes were already there, and was thinking  that i would be drilling the new holes in the hull of the valve at the same time.  I guess it would be a matter of measuring exact distance from the end of the tube to the center of the existing bottom hole, then figuring out the 90° from there.  That second part is where the intimidation comes in...  I did come across a  thread where the person didn't feel like lining up the 90° holes, and instead drilled new ones at 120° with the valve in the tube...  Any thoughts on this?

Any recommendations on a non-gauge block?  Do these also come with pin holes already tapped?   

EDIT:  Whoops!  I did not notice the "pinning the valve" sticky thread.  Perhaps I can adapt the same masking tape method...  I figure I would mark the tape in the middle where the center hole already is, and put the 90's at exactly .25 "tape lengths" on either side.  This would get me the 90, and I figure that I could just measure the length from the edge of the tube to get that dimension.  It does seem to me that 120 degrees would be stronger though.  Would I thread BOTH the valve and the tube, or just the valve?

[rsterne]

Forget the 120*, use the Disco valve holes.... You can use tape to figure out the position.... If you lack confidence in getting them in the right place, drill them undersize (eg. 1/4") deburr, install the valve with the bottom screw, screw in the side screws (hopefully you didn't get them so far out they won't fit through the 1/4" hole).... Scribe around the head of the screw, and use a Dremel to carefully enlarge the hole until the screw head just goes into it.... You can even work with a round file, a bit at a time.... Take your time, use care, and you should have no problem....

For the tank block screws, Ribbonstone wrote an excellent thread on how to lay out and drill them.... Search for it, or PM him....

If you decide on .22 cal, then you can get more power by increasing the port sizes.... The exhaust port in the valve can be angled towards the seat, the bottom corner rounded, and the diameter increased to at least 5/32".... The transfer port can be drill to 5/32" or 0.161", or you can use a poly port.... The barrel port can also be drilled out to 5/32" or 0.161", even 0.166".... some guys go to 11/64" (0.172") but that is pushing it, you may start damaging pellets on loading.... Making the gun breathe better will increase the FPE at any given pressure.... and of course you can always increase the pressure up to 1400-1500 psi and still not pop the 1.8K burst disc.... Over 30 FPE isn't to hard to get.... My 2260 HPA puts out 37 FPE (18.1 gr. @ 960), 40 shots from 13 CI on 1600 psi.... but uses a full length 2260 tube and reversed tank to take advantage of the larger plenum.... The ports are 0.166" straight through....



Bob

[aPpYe]

Huh!  Your drilling thing makes a lot of sense to me.  I think I can handle that pretty well.  I will be looking for the ribbonstone thread you mentioned this evening...

And and look at me back on the .22 bandwagon!  I figure that since a heavier pellet will keep its velocity for longer, then I can reach out even further than I could with a lighter pellet.  I am hoping for tight groups at 50 yards.

If I want more power down the road, I can always pick up a 2260 tube, or a hipac.  I am guessing the hipacs would be less safe though.  I have noticed that the HPA bombs (burst tubes, etc) I see here and there seem to share a commonality; they burst at the threads on the end of the tube where it is at its thinnest.

So tank blocks (rather than fittings, nipples, etc) are what I want then.  I saw a thread you started back in 2009 about how one can safely modify a standard (from uh ... "bow and arrow shootist" airguns I guess?) qb79 tank block for HPA use.  Do you still believe this to be the case?  Do you know better alternatives?  Any idea what they use on their PCP qb79's?  I see big warnings on their site about how one should NOT do this.  Would a novice machinist (myself, zero skills at the moment) be able to make one himself?  What about the reverse blocks I see here and there?  I do like the idea of a reverse tank on a longer tube, but I gather that going the "endcap-to-fittings-to-bottle" route is inherently less safe than going with a block, again due to the threads on the tube making it thinner and weaker ...  Thoughts?

Also, I really want to thank you for taking the time to answer my questions as you have been.  I have been reading a lot about this stuff these last couple of months and the name handle rsterne has popped up quite a bit with a veritable wealth of excellent information.

[rsterne]

I have used the stock QB79 tank block successfully, and I believe it to be safe with HPA, PROVIDED that the regulator is fitted with a 1.8K burst disc to prevent the tube (and the mounting screws) from ever seeing more pressure than it would with CO2 on hot day (1900 psi at 120*F).... Alternately, for more money, you can get one from JDS Airman that has the screws moved back, further from the end of the tube.... That, in conjunction with high-tensile 8-32 screws, is significantly stronger than the QG79 setup.... although I would still use a 1.8K burst disc.... Staying with a 1.8K disc will limit you to 1400-1500 psi, using more may blow the disc.... Sometimes you can get away with 1600, and sometimes you can't.... When a disc blows, I guarantee you will be looking for a change of shorts.... 

Reverse tank blocks are a custom only deal.... and NO I don't make them for sale.... You can do it with fittings, provided you do two things.... 1. use high pressure rated fittings... and 2. make sure you hang the tank securely from the tube, not just on the fittings.... I would advise you not to get too carried away with greed for FPE, because your 2400 tube, after you shorten it to get rid of the threads, will be less than 20cc of plenum.... Trying to push much past 20 FPE will lose efficiency, and may require an increase in regulator setpoint pressure to get back to the power you want....

Bob

[aPpYe]

Heh heh.  I wasn't gonna ask you to build one, I wouldn't want the liability either! Is it simple enough to make?  Would you be willing to provide measurements for your own designs?  I just discovered that my neighbor is a pretty accomplished machinist. He has this huge shop!  It is something to consider if i choose to go with the 2260 tube at some point.

Going with fittings, aren't I more at risk of failure, due to the fact that I am utilizing the part of the tube that is threaded, and therefore thinner than the non threaded part? 

I am not sure I follow about the plenum volume  though.  Earlier you said that I would have 24 cc "without a gauge block."   I took this to mean a block that does not have a port for a pressure gauge.  Am I misunderstanding this? Were you mistaken?

EDIT:  Aaaand I was up late last night messing with chairgun.  The app doesnt have a usable layout on my phone and I kinda gave up on it.  I installed it on my tablet and everything lines up!  Anyway, it seems that there is only negligible difference between 177 and 22 when it comes to target shooting at 50 yards.  Most of the lighter 177s lose a little more velocity and drift a little more in the wind  at 50 yards than a 14.3 grain jsb exact, but not by a huge margin.  Then I started comparing 10  grain 177s and the differences shrunk to almost nothing.   In fact, the 10.3  grain 177 JSB exact heavy has identical BC, POI, velocity and even  DRIFT at the target as the 14.3 grain .22 jsb exact, if the chairgun people are to be believed.

How long does it typically take, assuming one knows what he is doing, to change shims around and adjust between 1200 and 1400 psi? Can it be done repeatedly without messing things up?  Are the shims like a one time use kind of thing, so each adjustment digs into my pocket a little, and if so, how much?  Does the bottle have to be emptied each time?

[rsterne]

The threaded portion of the tube is not pressurized if you build the front adapter correctly, with the O-ring that seals it further back, behind the threads, where the tube is full thickness.... It is critical that the threads not be pressurized, whatever method you use, as they reduce the thickness of the tube by about half....

The "gauge block" I mentioned is like one on a Disco, ahead of the valve, and requiring a hole through the bottom (or side) of the tube.... The (gauge) mounting block, which must be sealed with two additional O-rings (one either side of the hole) is about an inch long, so takes up about 7 cc of volume.... dropping the 24cc down to about 17.... When you use a QB style tank block at the front of the tube, you have to cut off the threaded front portion of the tube, losing about an inch of length, so you still lose volume.... If you had a custom tank block that attached using the threads (like the reversed one on my 2260, that seals inside the threaded portion), you would not lose that volume....

Tank blocks are not very easy to make.... particularly the part that the regulator screws into.... certainly a job for a machine shop.... Here are photos of the reversed block on my 2260....



That one attaches using the threads at the front of the tube, using a drilled out 2240 CO2 nut, but seals on the full thickness portion behind the threads....

Bob

[aPpYe]

I get it, so tensile strength of the threaded section of the tube (and the cap) is plenty capable, so long as they are not also holding back the outward pressure of the compressed air as well.  Makes sense to me!  This means that a reverse tank is well within my capabilities.  The only real advantage I see with a block vs fittings is that the block can support the weight of the bottle by itself.  I would still want to support the other side of the bottle though. 

Anyway.  I think a more powerful .22 will have to wait maybe until next time I decide to undertake a project like this.  I think my mind is made up: CCS 2400kt with a 24" .177, peep sight, and a QB block with a 1400psi regulator, likely from mac1.  I am going to shoot for 17-18fpe with 10.3 jsb exact heavies or some such...  Now I just need to figure out what tank size I want. 

I plan on also having an RVA so I can tune for at least a couple different pellet weight classes, starting with the heavies at just below 900fps, some lighter pellets at the same velocity, and a low power setting for closer range plinking and fun with a really high shot count.   I will of course tune the higher velocities to the "knee" of the efficiency curve as I have seen you mention so many times!

[rsterne]

Properly tuned, at 17-18 FPE you should be able to get 100 shots from a 13 CI tank.... The bigger you go, the more shots.... but the heavier and longer the tank.... I personally would stay with the commonly available, and cheaper, 13 CI, for your 2400....

Bob

[BigTinBoat]

Properly tuned, at 17-18 FPE you should be able to get 100 shots from a 13 CI tank.... The bigger you go, the more shots.... but the heavier and longer the tank.... I personally would stay with the commonly available, and cheaper, 13 CI, for your 2400....

Bob

The KEY words.
Here's a chart form a member here (Happyhunter) on his reverse bottled .177 QB. Notice the huge difference in efficiency at 16.73FPE vs 17.41FPE - 40% more shots.

                                AR2078 /  13ci Bottle Reg’d @1375 psi / 10.34 gr JSB  / Clipped H-Spring
                                                                 

RVA (turns in              0          1           2          3          4            5            6             7            8            9             9.5
from min preload)

Velocity                     N/A      N/A       N/A       N/A       N/A       179.2     357.1      587.9      731.4     853.5      870.7

FPE                           N/A      N/A       N/A       N/A       N/A        .74         2.93        7.94        12.29     16.73      17.41
   
# Shots                    N/A      N/A        N/A      N/A       N/A         780        510         276         180       108           66

PSI used/shot          N/A       N/A        N/A      N/A       N/A        1.9           3             5              8          14            23

Shot Count              N/A      N/A         N/A      N/A       N/A        780        510         276          180        108          66

Efficiency                 N/A       N/A        N/A      N/A       N/A        0.42       1.11        1.62         1.65       1.34        0.85

[aPpYe]

That chart is one of the main things that started me down this road a couple of months back!  That, rsterne'a $200 PCP thread and a pic I saw of a crosman with a reverse bottle and hollow stock.  The shot counts blew me away, as the 15-20 "good shots" on a bell curve (and money) had previously sort of kept me away from PCP's... Here I am now!

That said, I finally pulled the trigger (pun intended) on a CCS 2400kt .177 with a 24" barrel, muzzle brake (are these just for show?) and a Williams peep sight.  I am hoping I can get close to those numbers with the smaller plenum...

I am leaning towards a 1400 psi 13/3000, maybe from mac1, and a standard qb79 block.  And I need to figure out what pump I want.

I am currently looking into RVA's and HDD's ...  Any thoughts/recommendations/advice on those?

I am hoping for some decent accuracy with the crosman barrel...  I may even go for a LW or other custom barrel of the accuracy drives me crazy.  I am discovering I am a bit of a nut in that department.

I am also fascinated by the idea of building a .22 on the same platform, but with a disco or 2260 tube using a gauge block.  Doing this, I would guess I can mount the tank in a "standard" direction, in place of the forestock.  Next year maybe.  I am also thinking about picking up an a avanti  499 for some indoor BB plinking.  One thing at a time though, unless someone feels like throwing money at me.  It's the wife's turn to save up for her camera.  Why she cares about that when there are guns to be had I haven't the slightest clue.  Something's wrong with her... 

[BigTinBoat]

I am currently looking into RVA's and HDD's ...  Any thoughts/recommendations/advice on those?

RVA?  drill and tap the end plug for a 10-32 bolt. Don't really believe in the "HDD's"

[aPpYe]

So that is all I would need to do?  I am assuming you are saying to do this rather than purchasing an aftermarket rva .. Doesn't the spring need to sit in a recession of sorts?  Or is that bolt size enough to push the spring forward?

As for the HDD's, I am seeing that this is something of a controversial (even contentious!) topic.  Even the believers report minimal gains.  I dunno.  I will have to check into it more this evening and decide for myself...

Also, is the stock hammer spring gonna get me the performance I want  or should I get something different?  Once I decide on a vendor to get my disco valve from (I want to avoid shipping as much as I can by getting things from the same vendor) I will order the rest of my parts.

[BigTinBoat]

So that is all I would need to do?  I am assuming you are saying to do this rather than purchasing an aftermarket rva .. Doesn't the spring need to sit in a recession of sorts?  Or is that bolt size enough to push the spring forward?

The stock end cap has a hole in it where the spring sits. I take a spent .22 casing and put it inside the spring. This is what the 10-32 bolt will push on.

Also, is the stock hammer spring gonna get me the performance I want  or should I get something different?  Once I decide on a vendor to get my disco valve from (I want to avoid shipping as much as I can by getting things from the same vendor) I will order the rest of my parts.

Stock hammer will be fine to 1400psi. You will probably have to get a stronger spring. If you search the 22XX HPA posts you should see the springs that different guys are using.

As far as the Disco Valve - I would get that right from Crosman. I think they are about $13. You can also get the springs there. I think the 2100 or 13XX springs are what you want. Get all your part #'s in order and then call them. It will be $4 shipping for everything from there.