>>63893070Where I'm from it's an old school boy trick to modify break-barrel air rifles to do the same thing.
The process involves replacing the mainspring with a stronger one, then using diabolo-type pellets with a large skirt which is filled with a paste made of grease and crushed up match heads.
The Diesel effect as the air heats up is enough ignite the propellant and massively boost the speed of the pellet.
Muzzle velocity is high enough to make a loud and clear supersonic snap.
The downside is that the rifling on regular air rifles aren't made for velocities even remotely that high, so the pellets don't stabilize property and the accuracy is complete shit.