The Three Stages of a Supersonic Gunpowder

Gunpowder is sensitive to shock and friction and heat. If it hits a certain value of all those things, it'll explode. The powder burning on the inside of the cartridge is a deflagration. That is a subsonic burning of the powder. And then that creates a pressure. Super sonic, not all the time, but in some cases a supersonic projectile. It can. Depending on the design of the barrel, the barrel length, the chamber pressure and a lot of stuff.