As a hobby machinist as well, I'm becoming very interested in airguns as well.
I hope to, one day, get into making/modifying them as a small business.
Would like to hear from you on PCP's in the ares of your thought on the different charging methods, maintenance, short falls, advantages, etc.
Charging methods are 3 stage and 4 stage hand pumps, SCUBA tanks, and high pressure air compressors. The hand pump is the cheapest and most portable. Air compressors and SCUBA are nice but in the event of grid failure/ bug out scenario would be useless
When I was shopping I had in mind what type of weapon would be most reliable and last longest in a survival bug out/ grid down situation and for me personally I chose air rifles. Conventional firearms have longer range and more power but there is an ammunition shortage and prices are skyrocketing and you are limited in the quantities you can buy. In a bug out situation you would be able to carry much more pellet ammo than conventional.
Also was the concern about the ammo getting wet, which, if it seeps in through the casing, could render the ammo useless.
Advantages of pellet ammo are: cheaper, lighter, take up only a fraction of the space that conventional ammo does and also (there is a difference of opinion on this subject) if you find your pellets on the ground and they are not deformed, the can be cleaned and re-used.
There is a debate about re-using pellet ammo. Every one has his opinion but I have cleaned and re-used pellets that were not deformed and they fired just fine.
Maintenance is simple. Regular barrel cleaning and corrosion protection with gun oil. PCP air guns should be kept charged at all times to protect the seals.
For survival hunting my 22 caliber Beeman RS2 is good for small game and the 9mm PCP is good for mid-sized,and, with a good shot, deer.