No one wants to hand pump from empty….it’s why we hate leaks and won’t go inside a working PCP unless we have to.
Do have time to think while you are pumping...and wondering what the *(&^ is going on when you have to pump fill from empty.
Might be wrong in some assumptions….but go ahead and think about it while you are pump filling.
Basically three pumps inside each other...like Russian nesting dolls. Stage 1 feeds stage 2 which feeds stage 3 (are some 4 stage pumps)...last stage is what feeds the rifle.
Stage 3 is tiny….not a whole lot of volume there.
Pump itself is a pressure vessel….it retains the pressure that’s lower than what is already in the rifle for use in the next pump stroke.
Check valves work on pressure difference...locking off high from low. Are two check valves in play, one in the rifle’s fill port/nipple and one at the end of the 3rd stage inside the pump.
When we start pumping from empty, those checks are open until we crate the pressure difference to close them. Until they are really sealed, there is some back flow.
Like 3 phases when starting from empty (it’s a bit like running track):
1. Starting: pump our azz off just to get up to speed.
2. Middle run: everything going to plan...pumping is pretty easy, gauges rises as expected, feels like progress.
3. Finish line: It gets progressively stiffer to pump. Only able to inject air that’s higher than what is already in the rifle, pumps strokes get stiffer (the working against the retained pressure in the pump) but only inject the pressure that's higher than what's already in the rifle.
Is a point where the effort to hand pump to higher pressure just isn’t worth it. Even with a great pump, few avenger shooters hand pump fill to it’s 4350psi max.
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