Crossman 2100 air gun

[Mortblanc]

Not only does the speed of pumping cause variation in the power level, so does the time lapse between pumping and firing.

Rapid pumping causes heat build up and affects pressure. Waiting for varied times before firing allows dissipation of heat and changes pressure. It is one of the reason why people think their pumpers are "leaking" while they stalk game.

I grew up using pumpers and learned all the "problems" along the way. I would often pump my rifle and lay it aside to cool before starting out.

I also wonder about the "accuracy testing" shown on the video. It was never stated how many pumps were used during the testing. It was also a very shaky shooting rest setup.

Personally, for messing about with targets I never used full power. I kept the sights adjusted for full power loads, pumped only three times rather than ten, and simply shot for group sized in a cluster I knew would fall below line of sight. sometimes I used a double target, on to aim at and one to show strike.

I did discover that my old pumper was most accurate with three pumps, and that was my "target load".