By now, most everyone is familiar with the .300 AAC Blackout. Designed to work in USGI magazines, the .300 BLK uses the same diameter brass as .223 Rem., but with a larger projectile and attendant change in neck, shoulder, etc. It offers .30-caliber performance while keeping to traditional magazines and bolts.
HPR Ammunition offers several different configurations for this new round, including this 110-grain FMJ offering. Designed for maximum velocity, this light projectile achieves 2,000 FPS at the muzzle and sheds about half that speed at 300 yards.
Overall length of the FMJ cartridge is surprisingly short—it's barely longer than standard .223 Rem. brass—so a quick function-check to ensure it works with your preferred platform might be a good idea. Given the quality components that go into this ammunition, once fit is confirmed it should work just fine.