Haven’t checked but there has to be a rechargeable electrical portable compressor that one can use in the field. Or an apparatus that allows multiple co2 canisters to recharge the guns compressed air reservoir. I’ve seen commercials on tv for portable air pressure tools that look like a cheap drill hooked up to a device which compresses air to refill a flat tire.
If not...someone could easily invent one. IMHO
Well, we were talking about Lewis and Clark’s air rifles, not modern pre-charged pneumatic (PCP) guns, so they didn’t have portable rechargeable electric anything. There are hand pumps that will get modern PCPs up to pressure, but it’s a lot of work. Those tire-inflators won’t do you any good at all, since PCP reservoir pressures go into the thousands of psi.