New QB 78 on HPA - (Now .25 cal)

[rsterne]

I've started working on another QB 78 setup to run on HPA.... The twist on this one is that the tank is reversed and will act as the forestock.... I did this on my Hayabusa project, and the QB 78 main tube was just the right length.... I'm using a 13 CI Ninja 3000 psi tank regulated to about 1600 psi and equipped with a 1.8K burst disc.... The tank block is machined from a block of 1" thick 6061-T6 aluminum that measures 1.37" x 2.63".... It is wide enough for a 3-groove Picatinny rail on the bottom for mounting a bipod and/or sling.... The tank is tucked up against the bottom of the main tube with minimal clearance.... The assembly attaches to the front of the main tube using the stock knurled nut with the hole enlarged to 1/2".... That is the only modification to the gun necessary to attach the tank, other than shortening the stock....



There is a brass fitting with O-ring that fits into the front of the QB main tube and is retained by the knurled nut.... The O-ring is moved to behind the threaded part of the tube for additional strength.... That fitting is attached to the tank block using a steel 1/8" NPT hex pipe nipple, with the knurled nut captured in between and free to rotate.... Below where the nipple screws into the block I machined a standard paintball fitting that the regulator output of the tank screws into.... There is a pin that presses on the pin valve in the regulator to open it.... The air passes around that pin and travels vertically through the block via a 1/8" hole to where the pipe nipple is.... and then from there into the main tube.... The bottom of the 1/8" hole is plugged by a 1/4" long 10-32 low profile SHCS recessed flush with the grooves in the Picatinny rail, and sealed by an O-ring....



Also in the photo above is the highly moddified QB valve.... Basically, once you open up the front of the valve, all it does is provide a place for the spring to sit.... With that in mind, I machined away all the extra material, so the valve is now the entire volume of the main tube, about 50cc including the valve area.... This is a large enough volume of regulated air to support up to 50 FPE shots without losing efficiency.... Since the eventual plan is for this gun to be converted to .25 cal, that is ideal for my purposes....

Bob

[Ribbonstone]

Like the machine work...the reverse block is a nice creation. Can't quite visualize the stocked end product but believe it could work out quite nice.  Rather than angled lines, accentuate the roundness of the tank/fore end?

Do think 50fp in .25 is doable (you might see near that in .22 with heavy weights)...and agree about having a large volume of pre-pressurized "on deck" air.

[rsterne]

I got the stock shortened today and everything bolted together for the first time.... and there were no leaks.... Here's what it looks like sitting on a bipod....



I made the barrel band later in the day but it's not in this photo.... It fits in the recess in the top front of the tank block.... I machined the extra notch in the breech to hold the bolt back as this gun will be "cock on open" and it makes sure there is lots of room to load the pellet.... I also machined recesses in the breech and valve for a poly transfer port and finished modifying the valve, installing a Delrin seat on the poppet and boring the valve out around it for increased flow.... I also eased the corner at the bottom of the exhaust port and drilled the valve throat out to 0.223".... This gun will use the new hammer I developed for the last QB 78 I built....



You can see the extra cocking notch for the bolt in that photo.... The upper hammer and cocking block are stock.... the lower ones are the new ones.... The sear catch point is moved forward 0.20" to increase the hammer travel, and the back of the hammer is shortened the same amount.... The spring guide is shortened about 1/8" and there is a hole in the bottom of the spring recess in the hammer to miss it and allow the hammer to go all the way back until it touches the cocking block.... That gives maximum possible preload room for the hammer spring....

I will be making a preload adjuster for this gun, but I haven't yet decided if I will just make it off center, or make a new rear block with screws top and bottom to retain it and the adjuster on the centerline.... I'll have a think on that tomorrow....

Bob

[Ribbonstone]

Really looks pretty darned good...got me fired up to play with QBs once again.

[SciGuy]

Your work with QBs is always great. 

[rsterne]

I did a bit more work on this gun today, sorted out the velocity adjuster and installed the barrel band.... Here are the photos....



The tank block installation is now complete.... However, I still have to rebuild the regulator from it's current 850 psi to about 1600.... I decided to install the hammer spring preload adjuster off-center.... The set-screw opposite it presses on a small delrin rod that bears on the side of the adjusting screw to provide a "brake" so that it will hold it's adjustment.... I ground the head of the 10-24 Stainless steel adjusting screw so that it has an indicator point to make full turn adjustments easier to track....



The adjusting screw pushes on a 5/8" long piece of steel round stock that is a sliding fit in the main tube.... If you back the screw out (or remove it), the gun shoots just under 500 fps with 14.3 gr pellets using the 850 psi regulator.... I kept shortening the sliding block until it was the correct length to achieve this.... There is very little preload on the hammer spring set up that way.... From there, I can turn the screw in 11 turns before the bolt can no longer be pulled back to engage the rear cocking notch in the breech.... I can actually go three more turns before the hammer runs up against the cocking block for a total of 14 turns of adjustment.... Should I need the last three turns of preload (highly unlikely) I can machine the cocking notch in the breech ahead more and still have sufficient room to load even the longest pellets....

I did enough shooting to assess the velocity adjuster.... Using 15.9 gr. JSB Exacts, with the adjuster backed out all the way I got about 450 fps.... In 1 turn, it increased to ~600 fps.... At 2 turns in, it was about 710 fps.... 3 turns in, the velocity was 790 fps.... and 4 turns in, it was 805 fps.... Turning it in more after that did nothing to the velocity, it just made the gun louder and used more air.... In other words, I have 7 turns of adjustment left to allow for higher pressures, which based on my previous experience should be more than enough to handle 1600 psi.... I don't want to run more pressure than that, as I want to still run the 1.8K burst disc on the downstream side of the regulator for safety.... It's beginnning to look like this gun breathes pretty well.... as I'm up to 23 FPE running only 850 psi.... That's stock Disco power at half the pressure....

Bob

[rsterne]

Well today I got to see what this thing would do.... I reset the regulator to 1600 psi, reassembled the gun, grabbed a tin of 18.1 gr. JSB Exact Heavies, and started shooting.... The velocity peaked at about 940 fps, just over 35 FPE, which is pretty decent for that weight pellet on 1600 psi.... I started with the hammer spring tension all the way in, shot 2-3 shots, then backed it out a turn, recording the velocities.... I stopped at 8 turns out.... For the first couple of turns out, the velocity didn't change at all, so I then started shooting strings at 2 turns out.... shot a string and then backed it out another turn, until it started to drop off the plateau at 5 turns out.... Here are the results....



Note how the efficiency climbs as you reduce the hammer strike, even though the velocity hardly changes.... It shows how important this type of testing is in a regulated PCP to not just waste air.... At 2 turns out I only got about 20 shots, at 3 turns out about 30, and at 4 turns out I could get 40 shots from a 3000 psi fill.... That's double the shot count with only a 7 fps loss of velocity.... One more turn out I lost about 30 fps but got 60 shots and the efficiency climbed to 1.32 FPE/CI.... That was a really exciting piece of news because that was 5 fps higher velocity than my previous QB78 was getting at an efficiency of 1.20 FPE/CI when tuned for the same shot count....

To say I'm pleased with the performance of this new gun would be an understatement.... It will be interesting to see what it can do when I get a .25 cal barrel for it.... If I was tuning it for these pellets I would try 4.5 turns out on the spring preload.... I would expect about 50 shots at about 34 FPE tuned that way (~920 fps with 18 gr. JSBs)....

EDITED to add heavier pellets:

I turned the hammer preload in to 3 turns out (to allow for heavier pellets to max out) and got the following results....

18.1 gr. JSB Heavies - 934 fps - 35.1 FPE
21.0 gr. H&N Baracudas - 890 fps - 36.9 FPE
25.3 gr. JSB Monsters - 832 fps - 38.9 FPE
28.4 gr. EunJin Domes - 799 fps - 40.3 FPE
32.1 gr. EunJin Points - 768 fps - 42.1 FPE

Bob

[Ribbonstone]

Pretty darned sweet!

+40 foot pounds with 1600psi is certainly moving right along, being in the middle 30's with standard type pellets is impressive.

[rsterne]

I think one of the best parts of this gun is the 1.32 FPE/CI.... That works out to 12.4 Barcc/FPE at 32.6 FPE with the 18.1 gr. JSB @ 900 fps.... pretty good for a regulated PCP.... I've never achieved efficency that high in .22 cal at that power level before.... (except in my Hayabusa).... 

Bob

[airpuffhunter]

great post very informative.
the info you produce is always good.
thank you Bob

[airpuffhunter]

now that you have done many mods for power,
is it possible to mount the .310 barrel on this gun to see how it performs?
to what pressure can the setup be bring up to?

[rsterne]

I will be changing to a .25 cal LW barrel at some point.... This gun is limited to about 1600 psi because I want to maintain a 1.8K burst disc on the output side of the regulator for safety.... The stock tube is of unknown steel, so I don't want to exceed the maximum pressures that can be developed by CO2.... which is about 1900 psi at 120*F.... This is consistent with the pressure rating of CO2 tanks which is 1800 psi.... I simply don't feel comfortable running a QB without a 1.8K burst disc....

Bob

[DFWdude]

The reverse block is neat, out of the box thinking and engineering

[TimmyMac1]

Best to trade the reg out. Ninja uses bellevilles on the Tanks that are 1200 and above, so rather than playing *(&^ tring to shim up something that is gonna be near coil bound I would have Ninja do you a 1600 Reg and then swap the regs out. The 800 psi reg is still useable on any CO2 gun and a lot of other stuff. Getting 11-1200PSI would be easy but doubling may be more of a hassle than your imagining.
Ninja Regs are awesome but I do not mess with them. I just use them as delivered and they get the job done.
I used a 1400 PSI Ninja Regged 13 CI on my US FT for a Bronze in the Worlds Air Rifle HV Benchrest.

[rsterne]

I'm quite familiar with the Ninja regs, I have rebuilt lots of them, using both springs and Bellevilles.... Here is some data you may find useful if you want to tackle working on them.... I developed this chart, and there is, of course, a tolerance from regulator to regulator.... If you exceed the point where the lines end on the chart you can run into coil bind (or having the bellevilles come up solid).... which of course will result in no regulating action and the full tank pressure passing through to the gun.... NOT a good idea.... 



I don't use the coil spring on anything over 850 psi, I change over to Bellevilles at that point.... The housings are the same.... Ninja use two different Belleville washers, 0.032" (thick) and 0.022" (thin).... They use 10 of the thick ones and 1 or 2 thin ones on the ends.... plus flat shims, of course.... They are arranged as follows:

)) () () () () (( | |

 Anything over 1500-1600 psi will blow a 1.8K burst disc, and even a 1400 psi reg can do that at high temperatures or if the burst disc is on the low side of the tolerance range (~200 psi).... Above those pressures, you will need a 3K burst disc on the downstream (outlet) side, PROVIDING the gun is strong enough to withstand that, of course.... I present this information for use by those who know what they are doing.... As with anything HPA, if you don't know what you're doing, DON'T....

Bob

[TimmyMac1]

Good Post. Experience speaks. I learn something every day here and I'm expected to know these things. Well done!
I have had problems playing with the pressures of OTHER regs so I was not going to mess with sucess.  When they had reliablity issues I went 100% Ninja. You have made it clear the pressure change is a relatively simple affair. I'll look into getting extra bonnets and spring sets so I can switch things around.
The standard bonnet is unmarked, of course, and that is the 800-850 reg output they sell but I like to have all other bonnets marked with the PSI so I know if it isn't marked it is standard. I have extra standards because they go on all the tanks and will be the fix for ANY damaged threads but I want all the non-standard tanks I sell to say what pressure they are when I ship them out.
I was using mostly 1200 psi regs for my HPA guns but switched to 1400 psi on the higher power (20+ fpe)and I think 1200 will work best on 12 fpe.
I'll talk to Ninja today and find out if they will provide 1400 bonnets and bellevilles for that Pressure. I have too many 1200's and not enuf 800 or 14 so I think your solution may be the best approach to always have what people need.
It is nice that there is a high quality American Painball company that has their act together on all of their products. They have been very helpful with the quest to figure out how Regged stuff works best.
I revisited trying to get 12 fpe out of a 1200 psi HPA set-up using a transfer port restrictor in  a Light Varmint 10.5lbs Benchrest gun.
It gets about 20 shots per 250 psi of the Tanks pressure so the efficiency looks about on par with what you'de expect from a wimpish gun.
A bud is testing it this week and I'll know by Saturday whether I wasted more time on 12 fpe or finally got what I want. It has been quite frustrating trying to figure out what makes a 12 fpe gun tick right. The EV II has it figured out and I'm not going to be happy till I can match that type of performance.
Have you ever removed the shrader stem and spring to get a little more volume per shot?
On a lot of the HPA high power set-ups we get rid of the stem and the mass involved that pushes it to get more firing volume and flow.
I've got near 20,000 rounds thru Ninja Regs Now and I have yet to have any hiccups whatsoever. At serious matches I always have an extra tank ready to throw on the gun but I have never needed it. I watch the reg output gauge like a hawk and they only seem to get more conisistent as they run in. I fire one settling shot after a fill and then go to work.
A nice Combo is to get the 22CI tank ONLY from JDS Airman and Put the Ninja Reg in that for 50% more capacity than the 13ci.
Linzie did that for her US FT and it came out so we could screw one tank out and the other back in by just taking the air out of the gun. You can remove reg/tank from gun or just vessel from reg if your only changing capacity.
That is going to be how people want it and Ninja makes a really low profile Inlet now that lets us do just that.
They deserve the business as they do a great job.
One very cool thing Ninja sends with Every Reg is the Black thread cover which doubles as a Foster Female QC Dust cover. Check it out. It fits perfect.
They also just put out some tank covers I need to check out.

[rsterne]

I really love the Ninja regulators, I agree that their quality is first rate.... I have removed the pin valve and spring on guns where I didn't need the ability to remove a partially filled tank (eg. RWS/Hammerli 850) but I find that the response time of the regulator is WAYYYYYYY too slow for the ability of the regulator to top up the pressure to really affect the shot very much.... That's why I try and use a large plenum between the regulator and the valve (and good flow into the valve) when I'm in search of power.... It's not necessary when you are in the 20 FPE and below region (although it doesn't hurt).... because you can just bump up the regulator pressure a tiny bit to make up for the lack of volume.... When you are trying to get the maximum out of a gun, however, I like to have 1 cc of volume between the regulator and the valve seat for each FPE I'm trying to get if at all possible.... More than that is pretty much a waste, it doesn't buy you much.... If you haven't seen this thread, there is a lot of info there on my findings.... http://www.gatewaytoairguns.org/GTA/index.php/topic,21681.msg194333.html

If you just want the summary, here it is.... Here are the results, using JSB 18.1 gr. pellets and a 1500 psi regulator setpoint....

Tube......QB78.....QB79

Low..........872........805
High.........885........817
Avg fps.....880........811
Avg FPE....31.1......26.4
No.Shots.....40.........39
Total FPE...1245....1031
PSI Used...1550....1550
Vol Used....1390....1390
Efficiency...0.90.....0.74

That was done with a valve with the front end opened right up so there was lots of flow into the valve.... If that isn't done, the difference between the QB78 and QB79 is less.... Here is a chart on the theoretical effect of plenum volume on the potential FPE.... It assumes that all of the plenum volume is available to keep the pressure up in the valve....



That is based on the average pressure available during the shot, which drops as the volume between the regulator and valve seat drops.... You can see how little gain there is to be made above 1 cc per FPE.... in fact to gain as much as you do going from 40 cc to 50 cc you have to go all the way to 100 cc.... One thing I now spend a LOT of time on with my regulated PCPs is getting the balance right between the regulator output pressure and the hammer spring preload.... If you add hammer strike, you just waste air, and the effects of regulator "creep" are quite noticiable.... If the hammer strike is too light, then the effects of the regulator "creep" are reversed (ie the velocity increases as you shoot), and then the velocity goes UP significantly below the regulator setpoint.... When you get it just right, you are working right at the top of a bell-curve throughout the entire shot string, with the regulated portion being just to the "left" of the peak.... That will virtually eliminate any velocity change due to regulator "creep" and will extend the shot string a couple of hundred psi below the setpoint.... all the while giving GREAT efficiency....

Tim.... Just thinking about your 12 FPE gun.... What happens to the velocity DURING the shot string above the setpoint?.... and what happens when you shoot BELOW the regulator setpoint?.... That will tell you what you need to do with the regulator pressure.... On my RWS 850, I played with changes as small as 10-20 psi to optimize it....

Bob

[rsterne]

I finally got back to this project the last couple of days.... I made a chambering reamer for the .25 cal Lothar Walther barrel and cut the chamber.... The forward pilot portion of the reamer is 0.243" diameter and rides on the rifling lands.... Then there is a 2* tapered section and the chamber portion is 0.255" diameter.... I then machined down the portion that inserts into the breech, milled the flats on it, machined in the transfer port and the O-ring grooves.... I then crowned it and polished it in preparation for bluing....



The photo above shows the bottom of the barrel and breech and the chambering reamer.... Note the much larger (3/16") transfer port.... The next photo shows the top of the barrel and breech, and the bolt, which has been modified to .25 cal....



I made one mod to the breech, I added two 6-32 set screws on the sides at the rear of the barrel.... There are matching flats on the sides of the loading port.... That prevents the back of the barrel from moving, therefore stabilizing the barrel much better in the breech.... The bolt was actually cut off about 3/8" in front of the full diameter portion, drilled and tapped 8-32, and a short stud threaded in.... Then a piece of steel rod was drilled and tapped and threaded onto the stud to make a new front end for the bolt.... You can't even see the joint in the photo.... A new O-ring groove was machined in the appropriate location carrying a 1/4" O-ring stretched onto a few thou oversize diameter so that it seals in the 0.255" ID chambered portion of the barrel....

I still have to make a new 3/16" ID transfer port.... I have found that Teflon rod works extremely well once you determine the correct length to get a bit of "crush".... I hope to do that and assemble the gun for initial testing tomorrow....

Bob

[bradyman1]

I  looking forward to seeing what you can do with this gun.

[TimmyMac1]

Talked to Ray Yesterday,
The lasty batch of tanks regs and fill stations had the tiniest gauge I ever saw and I talked to Ninja's Ray yesterday and he told me that was a one time deal and they will be delivering all the tanks, regs and Yokes with the Quarter size gauge on the orders in house. A small change had the standard 3K Reg body switch so the gauge and inlet port are 180 degrees off eachother rather than 90 as before.
Another small change literally is the low profile Inlets they now deliver standard that will be low enough so a lot of tanks can now screw into the front of many guns without the inlet nipple interferring with the barrel. The same low profile inlet are available in black as the Male QC we now sell and it has the option of having a check piece and oring installed inside to become an inlet assembly.
We have some cool little rubber inlet covers we are supplying with the males when we sell them with the Check piece as a fill nipple assy. That really makes it a unit that is practical and tidy.
On the Female QC side Ninja are getting Foster Female QC's in 3K rating (Black) that have Male 1/8" NPT threads rather than the typical Female. This can be very handy to avoid multi-fitting inflation.
Ninja are a bunch of Can-Do guys and they go out of their way to avoid doing anything unsafe. Products you can trust from guys who do what they say they are gonna do and have the ultimate intimate product knowledge (in real time).

They also asked me how many 22 CI's I thought I could sell per year which tells me they are considering adding that to the product line. I told them it would be a good move and the product volume would build. The minimums are ridiculous from the tank maker but it could still happen if they see the demand. The problem is it is all pelletgunners and no painballers that would want it. Pellet is really a fraction of the market of painball.

USA made and very proud of the quality. To make the price right they have to go deep. They will see this thread. If you have something to add this is a good place for it.

Later

Tim