I've been doing searches for a while on this thread and others, but I'm not finding anything definitive. This isn't really aimed at parts availability or logistical advantages, it's more aimed at ballistics and lethality.

I've pretty much lost all wishes to utilize an alternative caliber AR because of how much modification is required, not to mention sketchy reliability and parts incompatibility. The platform wasn't designed for larger cartridges and this has been proven after years of poor results from rounds like the 6.8, 6.5, .50 Beowulf and others. They look great on paper, and they really are, but until someone builds a better rifle specifically for them I personally don't think it's wise to try and fit a family of 5 into a 4-seater. I believe LWRC's Six8 line of rifles are a step in the right direction as far as solving that problem, but until they're released we'll just have to improvise.

However, the .300 BLK has caught my attention for the same reasons as everyone else: magazine and BCG compatibility. It seems like a win-win with the heavier bullet, negligible recoil and no loss of reliability (Is this accurate? Has anyone heard of feeding/ejecting/magazine problems with the .300 that the 5.56 doesn't have?). However, I have no interest in SBRing or shooting suppressed, so the subsonic advantages and short barrel effectiveness aren't important to me. All I care about is that the round may have superior ballistics when compared to the 5.56. What I want to know is whether or not this is true.

My question is whether or not the 5.56 can hold its own in a supersonic, power-oriented comparison with the Blackout. Is it truly advantageous to make the switch when the only thing different is the barrel? Does the 5.56 have an advantage when it comes to range and accuracy? Which round tumbles better? Is the recoil still controllable? Perhaps most important of all, are two identical rifles with the different calibers equally reliable? What about in higher capacity magazines such as a quad-stack or drum? If the BLK falls short in this category, it's immediately off the table.

I think it's also important to add that this shouldn't be looked at from a hunting perspective; I'm talking about a fighting gun. Take all the reasons that you'd want the 5.56 for a worst-case scenario and compare them to the .300 BLK: does it stack up?

This has been debated in the past, but I wanted a fresh take on it and also wanted to take out some variables like shooting suppressed, short barrels and economic advantages. I could care less if 5.56 parts are more available or cheaper, that's obviously going to be true and not what this discussion is about. If you have any input, please share. I'd like all sides to have a say so I can come to an eventual conclusion.

Thanks for reading and have a good day.