Air IS mostly nitrogen, about 80%. And it's inert, which oxygen certainly isn't! Only reason I get nitrogen vs. compressed air is that my supplier keeps the N2 in stock, compressed air would be a special order. I'm sure if you checked with AA, they'd say no problem. Now I've heard of some guys running their guns on helium, supposed to give a big boost in power, but it leaks out, because of the molecules size, it leaks through almost anything.
Like I said, I've been running mine on N2 since I got it, had NO problems. One little piece of anecdotal info that's probably at least partly coincidence. My brother bought a Talon SS from Dano in TX. Dan said he had it set up to shoot in the low 900's with Kodiaks. When it came in, we filled it and proceeded to chrony it. VERY consistent high 900's, shot after shot. On the face of it, just using N2 instead of air shouldn't make that much difference. Lots of things probably contributed. The top hat was a little loose, maybe it moved when I tightened it. I'm over 1500 ft. here, Dan's close to sea level. I think the biggest difference was introduced moisture. Dan fills with a pump, industrial gases are generally bone dry. My opinion is that the introduced moisture has a braking effect. I will say Dan did an incredible job setting up that Talon. I think we fired something like 50 or more shots from a 3K psi fill, velocity dropped less than 20 fps, and pressure only went down 800 psi. Even with the custom valve in mine, I don't do that well.
Congrats on that S400, I've heard nothing but good things about those rifles. The Xtra is a 30+ fpe .22, isn't it? I can't see going back, although Dan and Kirby have both done it. You're right, not enough challenge, just back up another 20! Or switch to a smaller target :-). Later.
Dave
