Is this totally a matter of semantics?.... The pumpers most of us are used to are "pump and dump" where the valve ends up empty after every shot.... Most people know that if you pump too much, eventually you get some air left over, which we call "retained air".... Most of the time this is a nuisance, but by careful tuning you can achieve some cool things.... I have a 2289/2200 based Carbine that is tuned to shoot 1 shot of 600 fps (14.3 gr.) from 10 pumps or two from 20 pumps.... The first shot is quite quiet, and leaves enough air in the valve for a second shot of the same velocity....
Steve in NC has spent a lot of time developing his "AC392s" (for Air Conserving, based on the Benjamin 392) which have a larger than usual valve volume and a HDD, which you pump to maybe 1200-1500 psi, and then shoot like a PCP, adding air when you have to / feel like it.... By using an RVA you can tune the gun to deliver, for example 750 fps on 5 pumps, 700 on 4, 650 on 3, etc.... Those are "additional" pumps to top the reservoir back up to the design pressure, so they are at the high end of the effort scale.... With careful tuning, you can even get 2-3 shots (more on lower powers) without pumping in between.... This is where the gun begins to transition (IMO) into a PCP with an onboard pump, like a poor mans FX Independence....
What do you think they are?.... More importantly, do they interest you at all, or do you think a pumper should just dump all the air on every shot?.... I've been reconsidering them lately, and I can see the merit in not blowing air out the barrel that does little (or nothing) to accelerate the pellet.... One thing I did learn in a discussion with Steve is that having the valve in any pneumatic (SSP, MSP, PCP, even CO2) stay open after the pellet has travelled half the barrel length is BAD for efficiency....
Bob
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