If 7.5" barrel was your only choice, which caliber whould you choose between 300 Black out and 5.56 and why? Yes we all know 11.5" is better.
P.S, no right or wrong answers here just opinions, because the research is also inconclusive, each has its strengths and weaknesses in close quarters.
Personally I prefer the 300 BO subsonic unsuppressed. How about you and why?
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300blk for me. I understand it’s more suitable for shorter barrels.
But on the other hand, 5.56 out of a 7.5” in a CQB situation would at least give the bad guy a nasty powder burn if you somehow miss with the bullet? My 10.5” 5.56 is quite a flamethrower. I imagine the 7.5” would be even more so.
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300 blk all the way. With can, if possible. Super or subs to taste. A 5.56 at that length is more of a flashbang than a rifle.
I use some very basic and likely oversimplified math for barrel length comparisons. Each inch of 300blk barrel has roughly the same interior expansion volume as a 1.8" of 5.56. So for example, 10" 300blk is crudely equivalent to 18" of 5.56. Math is (7.62^2) / (5.56^2) ~= 1.88, which I round down to 1.8 because I don’t fully trust the accuracy of this comparison. It’s not perfect, but if you look at energy tables per barrel length the conversion is decent. Doesn’t hold up for super short or long, but in the middle it’s a reasonable rule of thumb.
7.5" 300blk ~= 13.5" 5.56. That’s plenty for 300, noisy for 5.56.
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It’s really not a good comparison at that length imho 300 hands down 
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My 7.5" 5.56 upper keyholes so bad, that some rounds miss a man sized silhouette target at 25 yrds. Then next round is a bullseye.
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What Gr. or all?
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.300, from what little I know. Suppressed if possible.
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Well it could be the operator 
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Yeah, the 8” Marauder (in 5.56) throws flame as long as the firearm out the front of it - enough you can easily see it in the daytime.
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Like I said while my opinion is that for close quarters (home), the 7.5" 300BO 200gr Subsonic, is a logical choice for me. Yet there are those with compelling reasons that I may be wrong, like this fellow…
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I think you’re right on. A subsonic 300blk is basically a pointy 45 ACP. Same weight, same speed, same energy. Get some good ammo that’ll open up at those slow speeds and I can’t see how you’re that far off. Is it full on rifle performance? No. But rifles are not as good as a full spread of claymores either. Kinda depends where you want to draw the line.
Back in reality, if for some reason you need to reach out further, drop a mag of 300blk supers into the same gun and you’re good there, too. According to the various barrel length studies I can find, a 7.5" 5.56 with full power 55gr ammo will give you roughly 2200 fps, which is 591 ft-lbs. of muzzle energy. So you’re down to the subsonic 300 blk energy levels anyway, plus a complimentary flashbang with every shot. I struggle to see how 5.56 would be a better choice in this setup. It’s not a nerf gun, but it sure seems like a suboptimal solution. Better against body armor? Ok? If the local crackheads smashing windows start rocking out plate carriers, I think I’ve got bigger issues.
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PSA 7.5" 300BO in its post-brace June 1st “Pistol Compliant State”. Still evolving, still in need of a light, and perhaps an optics change. Incidentally, can anyone guess the current optics?
P.S. I consider this a Cheek-Jaw braced Pistol
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tbh… pistol tubes are dangerous and i would never use one. i like full length (pistol gas) 300 supersonic and the normal full length 556 carbines the most… 7.5” just worked best with 556 in my experience
Every person is entitled to his or her opinion, especially on guns. What I recommend is that you author a new topic about the attributes of the Rifle-Length AR15. One is no better than the other, they simply reside in different classes in their respective roles.
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What I recommend is that you focus on i specifically said “pistol tubes”… i have no issues with length… my 7’5” is a sewing machine, so is my 16”… PISTOL TUBES are dangerous that’s just a simple fact i don’t need to write a book about it you just showed a better example than i could imagine with a tactical T Rex video.
I doubt it. In my 30 year career as a weapons specialist I must have had over 25000 A1’S & 2’S cross my inspection either personally or as weapon officer in charge. And never had I heard of an injury report involving a buffer tube and spring. I’ve heard of Beretta slides hitting people in the face, fingers chambered in M14’s, 1911 hammers dropped with a live round hitting personal, hands getting caught in 20mm MG feeders, fingers cut off in ship’s main gun loaders, Browning 50 BMG recoil spring impaling sailors during incorrect disassembly, I even personally shot a signalmen accidentally on an adjacent fueling ship in high winds firing a 45/70 line throwing gun attached to a 5Lb rubber projectile. But never have I seen a service wide message on the mishaps or injuries caused by AR buffer tube springs. Unless of course they were used in an unnatural way. But hay maybe there is one out there that did. I can only speak to Milspec parts, today with all the buget option compromised parts and wannabe’s that but them, maybe your right and in the know…
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they wouldn’t put a foam thing around something safe to use, it’s like they are trying to protect.
I want to thank everyone with a big thumbs-up because you provided objective real-world input.
Stop with the back and forth. Only warning.
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