I suppose, in the kingdom of the blind, the one-eyed is sometimes thought to be king.LOL
1) An electric or fuel operated high pressure air compressor. This is an expensive option and usually used by some clubs, gun shops and dive shops.Anyway... so what are the 'sources' of 'air' for a PCP airgun?
2) A scuba/scba tank. Item 1 is used to fill this. This is what I use. Thiis is a cheap and efficient option. You can get it filled at the local firestation or dive shop
3) The three stage manual pump that looks like a bicycle pump. This is the cheapest option of the lot but unlike the first two that provide dry, breathing quality air, this does permit a small percentage of moisture into the guns air reservoir which may create a problem in the valve/regulator mechanism or even start oxidising the air reservoir in the long run.
Provided you use the right adaptor, you can fill most of the current production PCP''s with the handpump.And is the hand pump usable with all guns?
Most of the current production PCPs are filled to 200 BAR / 3000 PSI (approx.) and the hand pumps are designed to pressurise upto 250 BAR if I am not mistaken. Filling guns with tube reservoirs does not take much effort as their capacities are usually in the 70 to 100 cc range. However, those guns that use a 400 or 500 cc Buddy Bottle (smaller scuba tank carried by divers for use in an emergency) will take a lot more effort. However, this isn't difficult because one should not use the pump when it gets hot. It should be allowed to cool and this automatically gives you a 10 to 15 minute respite.