Spudinator wrote:The way I recall it, gas can not exceed the speed of sound at room temp, thus a projectile fired by said room temp gas cannot either.
That's not actually true. Gas can quite easily exceed the speed of sound at room temperature - it just has to not be at room temperature itself.
It is true to say that under practical restraints, a gas normally cannot expand faster than its SoS. These restraints include microscopic imperfections in the barrel - a supersonic flow hitting these forms a shockwave, and this spreading shockwave then disrupts supersonic gas flow through it, slowing it down.
For those reasons, it is reasonable to make the assumption that gas flow does not exceed the speed of sound for its temperature. However, that does not mean the gas in the system is the same temperature as the ambient gases outside the system.
Things such as adiabatic heating and shock effects can raise gas temperatures to the point that the internal speed of sound is significantly higher than that of outside the system. (That said, most spudguns do not harness these effects, and have a lower internal SoS.)
The AirForce Condor is actually marketed as a supersonic PCP - and you can be sure there'd be some stink if they weren't capable of it.
Yes, it's hard to go supersonic when your gas bottle is only at room temperature, but if you will, imagine the internal science of something that is capable of it somewhat like the spring piston airguns you've already mentioned.
The difference is that instead of the piston being a large spring driven lump of steel, it's replaced by the gases coming from the reservoir, which similarly compress and heat the gases ahead of them - those already between the pellet and valve.
This is also magnified to some extent by shock effects - sound waves travelling through the gasses in the barrel heat it. Progressive soundwaves travel through slightly warmer gas, thus travel faster, catching up with one another, eventually combining into a supersonic shock front.
The shock effect is well known, and can be observed in a laboratory using a "shock tube" - which is basically a pneumatic burst disc cannon without a projectile.
Anyway, as has been said - supersonic with room temperature air is hard, but not impossible if high pressures and good design are involved.
I know I'm one of the chief sceptics when it comes to debunking supersonic claims on this forum, but that's largely because many of the designs involved seem unlikely candidates to harness these effects.
A modified AirForce Condor however - damn, you'd better believe that's capable of it!
This post brought you by the "Ragnarok gets rather loquacious when tired" foundation.
) and then see if I can get a golfball supersonic. Getting the golfball supersonic will be a maybe. The marshmallow should be no problem.