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QB 79 hpa conversion help

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gosse_78:
I'm new to this fourm...i have a springer and a bunch of pump guns,love shooting them all,but looking to get into PCP.for starters,i would love to convert a 79 .22 to hpa.i know i need  the gun, a pump and a hpa paintball tank,but what else????? any recommendations or other things i need??????

Gary:
I thought about doing that myself. After reading many posts both here and other forums I came to the conclusion that unless a person wants a project instead of a rifle that you put together and go shooting to go for it. Without a lot of tinkering it will have a low shot count, fps. will be lower on every shot,etc.
got a Disco with the pump combo and I am pleased with the rifle,not so much with the pump. While the pump does work it has been a real pain,resealed it shortly after the warrenty ran out and have had it apart a couple of other times to clean the crud out of the check valve. A Hill or FX pump would be a better buy I think.
Gary

Ribbonstone:
Think you miss understook his post (or I did).  As it is a QB79, think he means an HPA tank rather than trying to compress air the tube. 13Ci HPA tank won't be guilty of a short shot count and won't be giving ever lowering speeds.

Personally, prefer the little 13CI tanks for the conversion.  I made the choice not to go over standard co2 type pressures, and usually run my HPA's with a tank set for 850PSI output. Even that low pressure generally shoots 5-10% faster than when using co2 (would turn a 600fps shooting co2 QB into a 650fps 85o psi HPA QB).  Other people have run them with HPA tanks set to give 100, 1200, or even 1400PSi and they've not reported any problems (may have been some problems, but they didn't report them).


The HPA tank won't just spin onto a QB79.  The gauge and the fill nipple sitck up too far to clear the barrel.  I just take off the barrel to put on the tank (or take out the gas block, mount the tank, reinstall the gas block with the tank mounted.

Sometimes, the gauge or the fill nipple end up sticking up and would block the barrel from being reinstalled.  A bit of shimming will let the tank tighten with the offending part not sticking up in the barrel's way.

POSSIBLE PROBLEMS:
1. Leaks from the gas block o-rings.  Air is "thinner" than co2, so it tends to find leaks that you don't notice on co2.  CO2 also tends to slightly well o-rings (sometimes that helps co2 leaks) but air does not.

2. If you use higher than normal co2 pressure as your tank output, don't mean woman and moan if your QB valve and/or seals die an early death. Ran one at 1200psi output for over a year with no problem, but decided to back off to a 850psi output tank.

3. You'll notice in the below picture that all the HPA guns have a brass on/off between the HPA tank and the rifle.  That on/off (by RAP4) has a gauge to read the output pressure and a burst disk. You don't NEED one, but it is nice to have for several reasons.

4. Even a 13CI tank is a pain to hand pump.

5. Neat thing is that you don't have to fill the HPA tank to 3000PSi to get full speed.  If the tank is filled to over the regulator's pressure, will get full speed (gun runs off the tank's output, not the tank itself). # of shots seems to be proportional... if you get 80 shots from 3K to 1K, you'd get about 40 from 2K to 1K.

Only one of these is a QB79, but did add blocks to 3 other QB's and run them on HPA tanks as well.  Depends on how the gun is set up, but the lower powered guns (12 foot pound area) can give about 100 shots per fill.  The big .25, set for  32 foot pounds, got about 42shots with that 1200psi tank.  With the 850psi tank I switched to,is down to 23 foot pounds but up to 60 shots.

gosse_78:
thank you Ribbonstone!!!you understood what i was getting at. what other mods have you done to your qb 79 to get 12 foot pounds?? how is that guns accuracy????can you use diferent mods such as the qb xp tune kit found on ^&$@_=s.com??

P.S. sorry for pickin your brain

Gary:
I sure missed it on that. Well thanks for not flaming me.
Gary

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