I am also looking at the issue of .22 vs. .25. One of the things affecting my thinking is that the local club in Southern California will allow nothing larger than .22 on their field target course.
I have always wanted to hook up a motor to a hand pump and let it slowly work like oil field Pumpjack. Up and down slowly over a long time. Let it take a week to fill my bottles for the next weekend.
Just seen pictures on the website and videos on Youtube: But the Mustang by Lobo Airguns is a cowboy style rifle that is on my list of things to buy someday.
I topped up my black 7oz C02 paintball tanks today. I shoot my Gauntlet gen 1 with CO2. I don't have hpa yet. CO2 works fine for my ten yard indoor range. 7oz tanks are 1.99999 inches in diameter so there is no requirement for tank testing.