Guess I'll go ahead and jump in here now. I've been filling my PCP's with nitrogen since I went to the Dark Side. Too lazy to pump, and because I live 5 miles past the middle of nowhere, scuba tanks were a major hassle, and expensive. I rent a 4500 psi tank from a local welding/industrial gas supplier. Made up my own fill station, this is what it looks like:
Tank rental is $85/yr., gas runs about $60. A tank lasts me at least 6 mo. Tank specs are 443 cu. ft. @ 4500 psi. Haven't actually checked, but I'm pretty sure that argon would be more expensive than nitrogen. Also, I could get plain compressed air from the same source, it would also be more expensive, since it would be rated for breathing air. No downside to using nitrogen performance wise, and in fact, it's actually a plus. Since there's no oxygen in it, there's no corrosion to gun parts or oxidizing of seals. And although I don't have any proof, it just feels like my guns shoot better.
The filling station I made up has a foster fitting on the end of the fill line, I swap out fill fittings as needed. One of those fittings is an SCBA fitting, so I can fill my 44 cu. ft. carbon fiber tank. Even with a fresh cylinder, I never actually get a full fill, but it's good enough for me.
You're right, safety is important, but the most important safety device is the one between your ears. I don't use a regulator on my system, I throttle my fill valve and watch the fill gauge. So no distractions allowed when I'm filling! Unfortunately, I shoot alone almost all the time, so that's not a problem :-(. And everything in my system is rated for at least 5000 psi. Don't know if it's possible to do the same with a 6K psi tank or not. Depending on what rifle you have, you might be able to buy a spare tank for it, so that might be another option. Hope that helps, if you have any more questions, you know where to find the answers :-). Later.
Dave
