The threads on the cartridge are not tapered, so you will have to seal them by soldering or installing an O-ring somehow.... You might get away with glue or sealant of some kind, but I have never had success sealing HPA with those.... I soldered the cartridge into the brass gauge adapter on my pumper.... Bob
If I can't use the co2 approach, how thick do aluminum walls (cylinder) need to be to withstand (2100 PSI+) 145 bar - safely?