QB78d long Co2 tube

[rsterne]

I would stay under 1800 psi on HPA with a QB.... CO2 can reach that pressure at 120*F, so IN THEORY the gun should be able to handle that.... The problem with regulated HPA is that if you have a regulator failure the gun will see whatever pressure is in the tank.... would could easily be 3000 psi.... even 4500 if you are using a 300 bar Carbon tank.... I would highly recommend that if you are using HPA on a QB that you make sure there is a 1.8K burst disc on the downstream side of the regulator.... That limits you to about 1500-1600 psi so you won't blow the disc.... If you are only filling with a hand pump, I might consider using 1800 psi.... but you will need to shim the hammer spring, replace it, or increase the hammer strike in some way to use that much pressure....

Bob

[SeanMP]

Bob, I think the question was what do you have to do to utilize the full potential of the aftermarket 3000 psi tube. I can't comment on any specifics beyond the stock tube

[rsterne]

Actually haven't a clue, never been up to those pressures.... You would certainly need to lean on the hammer spring quite a bit to be able to utilize a 3000 psi fill without the velocity dropping like a stone because of valve lock.... It is POSSIBLE you might get there by shimming the stock spring to the maximum, maybe combined with shortening the back of the hammer and the spring guide.... but I wouldn't guarantee it.... I had about 1/8" more preload available on the hammer spring than what I needed for 1600 psi on the last QB I did.... I have no idea if that would be enough for 3000 psi or not....

If you can't get there with a stock hammer spring and shimming (or using an RVA) then you would have to find a stronger spring.... The only one I have found so far that will fit is a 0.360" OD x 0.059" wire Trakar spring and it is too big to fit in a stock hammer.... Since they are hardened, now you are into making a new hammer to fit the bigger spring.... and on it goes....

As far as the safety of the valve attachment system, I would have to do the math on that to determine the safety margin (if any) at 3000 psi....

Bob

[just missed]

Planning on sticking with Co2 and in the event I as to try HPA wouldn't fill high pressure, staying under 500 fps. Even with the bulk filling Co2 I will be working with a crony to keep it under and looking for advise on how to keep it there.