-> That's a neat idea, but I think I'd stay away from the freon bottles.
Heck Gerald, freon tanks are SAFE compared to the junk some people use!
I've pumped the 15 pound size of freon tank to well over 400 PSI with no
sign of strain.  Hydrostatic testing is of course the way to go, but
putting the tank out in the boonies where it can blow up if it likes is
the next best thing.  We DO want to err on the side of safety but if you
pump a tank to 400 PSI it's pretty dang safe for 125!
-> 300 lbs before the plastic valve popped out. Have no idea how much
Do NOT mess with the newer "safety" freon bottles those plastic valves
are MADE to blow up.  Use the old style and you're safe.  They have a
blowout plug in the bottom which will not let the tank itself split, and
are good for 125 PSI.
Also don't use water heater tanks unless you like to live dangerously,
ESPECIALLY if your name is Jerry!    *I* use one but then I've
pumped it to 350+PSI even after I'd welded up several holes, and I limit
it to 100PSI and don't trust it any further than I can throw it. 
Do as I say, not as I do!  I'm old and don't CARE anymore.
 ^..^
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