From thetruthaboutguns.com:

The 6.8 SPC and 300 BLK cartridges were designed for two very different jobs. 6.8 SPC was designed to be a longer range cartridge, while 300 BLK was designed to be a shorter range cartridge that worked well with a silencer.

I get this a lot, actually. And its a valid question — what makes 300 BLK so much better than the other calibers available for the AR platform? And is it actually better? So here’s the truth…

It depends on what you want to do.

I’m going to break this into three categories, encompassing everything a shooter should consider when choosing a caliber: performance, compatibility and availability.