The users of these two weapons aren't likely to care about bullet weights and muzzle velocities.

A 300 Blackout SBR is a rifle firing a rifle cartridge. If rifle calibers are allowed at the range, then they're fine. If they're not allowed, then this rifle isn't allowed.

A 10mm Auto carbine is firing a pistol cartridge. If pistol caliber carbines are allowed at the range, then they're fine. If they aren't allowed, then the rifle isn't allowed.


The easy answer is that if a cartridge was initially developed for use in a handgun, then it's a pistol caliber. If the cartridge was initially developed for use in a rifle or carbine, then it's a rifle caliber. There's little to benefit by making this more complicated than it needs to be.