how much pressure will a STANDARD QB78 take?
i want to pump my standard AB78 up with air (via hand pump) instead of CO2.
never squat down while wearing your spurs...will rogers
..without any prep, just filled a co2 QB with air (memory has it as being 1200psi) and shooting the two side by side for 8 shots.
Probably the gun being tuned for co2 was quite wasteful of air, but if I had just fired 3 shots (the top 3), refilled to 1200, shot 3 more, refilled to 1200 and shot 2 more, the groups would be about the same size.
Co2 exists as liquid and gas when the gun is filled. Each shot taps off some gas, and the liquid replaces that gas, so the pressure is pretty constant over a long number of shots.
Air starts out at 1200psi and each shot lowers the gas pressure in the gun...there is no replacement for liquid as there is with co2. So each shot is taken with lower and lower pressure.
Evidently that valve could handle three shots with a reasonable consistency (it self regulated for a short time), but as gas pressure dropped, the valve just couldn't make up for the lower pressure.
Some reasons this experiment might be a bad idea:
Co2 guns tend to run wet with lube. Compressing air in a cylinder lubed with petroleum based products is not a great idea. PROBABLY if you compress slowly and only to 1200, nothing bad would happen...but if you gun goes "boom" don't blame me.
CO2 seals tend to leak air. Air is just thinner and doesn't have the quality of slightly swelling o-rings that co2 has.