Maximum rate of expansion
Does there reach a point when it doesnt matter how high the pressure your using or lengh of barrel ect
does the high pressure air reaches some sort of terminal velocity ? ie speed of sound in wich case the only way to speed it up is to increase the temperature ie powder burning
just curious to know if its possible with 5000psi tank and big bore valve and long barrel if you could push a pellet/bullet shaped for supersonic into that sort of speed region
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Hey Colin,
A few random memory bits come to mind when I read your question. I believe one of your fellow countryman with the ID of Dave(Spooky) talked about a practical limit of around 340 MPs (around 1080fps) with air as the driving force (due to the speed of sound) without a huge increase in pressure. The upper limit with air is around 1400fps (he was playing with 400 bar and above). That’s why burning powder ie. increasing temperature can get the velocity much higher (the hot gas jet just after the muzzle is around 6000fps). Dave was using about 6000 psi for his airgun. The valve design is special too because it has to be able to dump huge volume fast before the projectile starts to move.
Length of the barrel is important but I don’t recall seeing any study similar to the powder burners where people would chop the barrel one inch at a time and measure the MZ vel. because no one had rifled an airgun barrel longer than a few feet I guess. Some how, the order of magnitude figure of over 10 feet came to mind.
Btw, Spooky also mentioned the speed of sound in helium at 10C is 900+ MPs. 😉
All the best with your research.