Crossman 760-A velocity

[MiG25]

Ran a Crossman 760-A over the chronograph.

The rule of thumb was always 10 pumps for maximum power.

Max velocity of 465fps was reach with 5 pumps and SLOWED down a bit after that. 4 pumps was almost as fast and 20% more efficient.

From now on it will get 4 pumps.

 

[SomebodyTookMyName]

Interesting find! I'm betting that the extra pressure from 6+ pumps is causing the valve to snap shut faster than needed and cutting off the air flow before the pellet has left the barrel.

I souped up an old Crosman multi-pump airgun (Airmaster-something I believe) quite a few years back by opening up the orifices where the air flows through, and then lightening the spring which returns the valve to the closed position, so that the air reservoir is forced to empty completely regardless of how many pumps it's given. If I recall correctly, I got it to around the 650-675 FPS range.

 

[HeadDamage]

That curve of pumps vs fps is normal. My 1322 is 440fps with 10 pumps and 499fps with 20.