Originally Posted by ThunderCactus
I think you should power your GBB pistols with oxygen instead of propane.
I actually had someone bitch me out for making a sh*tty adaptor because it wasn't threading onto a disposable oxygen bottle. Oxygen bottles have left handed threads that are otherwise similarly dimensioned to disposable propane bottles. A customer a few years ago wanted to use oxygen because the bottles are pressurized to 400psi (I think) instead of the 130psi on propane.
I was doodling around with the injector design around then and was considering how one might shoehorn enough oxygen into a propane bottle to make things dangerous and I couldn't come up with an easy way to get to a dangerous mix because the injector had such a small shot volume and air is about 80% inert gas.
The situation completely changes when it comes to a pure oxygen bottle pressurized to 400psi. Shooting 100% 400psi oxygen into a partially propane filled GBB mag can reach ideal gas mix conditions. All you need is a little liquid residue in a mag and you can reach high pressure (26atm!) ideal mix conditions.
As a bit of beer coaster estimation:
-room temp: 300k
-adiabatic flame temp of a propane oxy flame: 2800k
-plugging ideal gas law which works really well at high temps: 9.3x pressure factor
Some Gr 12 chemistry! Atoms indicated in lower case because I can't figure out subscript
-c3h8 + 5o2 ---> 3co2 + 4h2o (balanced formula for ideal combustion)
-6 moles on reactants : 7 moles for products
-assuming everything goes to vapor after combustion (pretty good assumption I think): 1.14x pressure factor
If you were working with reactants initially at atmospheric pressure you'd get a pressure of:
9.3 x 1.14 = 10.6 expansion factor = a mere 160psi
However you start off with things at 400psi (26.6atm!)
26.6atm x 10.6 = 282atm! = 4230psi!
Our crappy cast aluminum magazines are not engineered to contain a 4.2kpsi explosion...
Stay in school. All the stuff I used is high school level and it works in ideal gas situations far from condensation conditions.