Ammo cost, availability and the millions of civilian ARs will keep it around for a while. Military is developing that new 6.8 round but if not done right it could be another expensive DOA project. Design by committee is a recipe for disaster.
In my opinion and it might not be a popular one, 6.8 SPC II is the round that NATO should have adopted for their infantry issue carbines. Better performance and knock-down power out of shorter barrels at longer ranges compared to 5.56. It is better in every way. Plus, I’d take a 6.8 SPC over 308 all day long. Extra weight of 308 plus the extra weight of the ammo is a killer whether you’re hunting game or enemy combatants. Not to mention the case design of the 6.8 is so good that Federal chose it for the .224 Valkyrie which I love to shoot. The casing is also the advantage over a round like the 6.5 Grendel. The case also allows for thicker webbing between the lugs of the bolt which is huge when it comes to durability. Take a look at the extra brass in the base of the casing of the 6.8:
I’m not an expert on 300BLK but from all that I’ve read and been told by people who know more than I do, it is now simply the best cartridge for SMG style weapons. Pistol caliber rounds just can’t keep up. They’re quiet, made for short barrels and can reach out a bit when needed. I am really curious about penetration though. Is that a limitation of 300 blackout? From what I understand, it is velocity that you’re looking for when trying to penetrate barriers. And if that is the case then 300 BLK actually might not be the best “do everything within 200 yards” round. 95gr 6.8 SPC factory loads are leaving the muzzle at up to 2900 fps. Maybe someone can chime in here to educate me on this issue of penetration.
The 6.5 Creedmoor is definitely the way to go for large platform and it’s performance can justify the extra weight of the rifle and ammo. I think this is pretty well established.
So the question here seems to be, do we need something between the 300 BLK and 6.5 Creedmoor. If the 300 BLK lacks lethality through barriers then it could be that to cover all scenarios, we still need: SMGs in 300BLK, M4 style carbines in (maybe in 6.8) and a long range semi-auto solution in 6.5 Creedmoor.
Good topic and I’m very much looking forward to being educated on any false assumptions I’m making here.
Here is a great interview done by our very own @jburton talking to the man, the myth the legend, Mr. Chuck Pressburg about some of these points: https://www.arbuildjunkie.com/5-56-vs-7-62-chuck-pressburg/