1) My personal experience with .300BLK = 0
2) Buddy just built a .300BLK rifle ... maybe I’ll get to play with it.
3) Ballistics table says it’s a hair weaker than 7.62x39 ... 125gr @ 2200fps vs 124gr @ 2350fps.
If you’re looking for a ‘reach out and touch someone’ round, I don’t see .300BLK as answering the mail.
I've built two over the past 5 years and I too remain unconvinced. The big question will be how well it might perform in the squad's automatic weapon or LMG. Remember that both the most common rounds for the 5,56mm cartridge, the M193 and M855, were developed for the 20-inch barrels of the M16 and the M16A2. Those for the .30BO have been developed for ten to 16-inch barrels.
Nope, it's NOT a long-distance round; it is a believable carbine round, especially in a short-barrel PDW or with a suppressor. And it has been combat-proven with Special Forces in Afghanistan, where a pal in that line of work describes its effectiveness there as *having been in the four-figure range*- in excess of a thousand enemy KIA. I'd bet a lot were at night, with a suppressor.