What cans are we using on SBRs and AR pistols?

[WillBrink]

Your only selling point is defeating body armor,

That's a pretty big selling point to some, can't say that's a major issue I'd worry about.

and ammo availability, but now youre pigeon-holeing yourself to a couple specific loads?

If the rec is defeating BA, limits choices. If not, a wide range of choices from all major manufacturers exist now that will do 2200-2400+ fps (depending on weight) and offer excellent terminal ballistics exceeding that of any pistol in typical duty loads, pistol caliber carbine, or PDW, by a margin, in SD/HD distances and then some.

I tend to view it a PDW that's using a rifle bullet, and an effective one at that, some can't let go of the rifle aspect, and continue to compare to rifle. Compared to a 10" you are giving up something to be sure, not nearly as much as some seem think for the role of HD/SD/PDW by the easy to supply numbers.

For example, the Federal MK 318 Mod 0 (SOST) 62g is barrier blind design, does 2200 fps from a 7.5 inch barrel and performed very well in jello testing by wide margin to any pistol in typical duty loads, pistol caliber carbine, or PDW. While that's not the easiest load to find, again, major manufacturers offer various similar. Anyone claiming "just use a pistol caliber carbine" at this point has no credibility here.

There is an argument to be made for longer barrel ARs to be sure, but it's also an apples to oranges thing to me. Conclusion:

7.5" (or dare I even say, shorter!?), is vastly superior to any any pistol in typical duty loads, pistol caliber carbine, or PDW.

It is inferior to longer barrels depending on the role it's intended for, but not as inferior as some seem to believe.

300BLK would be more optimal all around, but 5.56 is much less $ to run (and that's no small thing these days!), far more available, and more then adequate terminal ballistics with the right loads, which are now common. No, it's not the most efficient use the 5.56

[Outlander Systems]

Given the discussion is regarding suppression, we’re dealing with polish blanket trick of barrel/suppressor.

A rebarrelling to .300 should set you back a whopping $150. .300 has become a lot more viable given the prices 5.56 has climbed to. Throw suppressors in the mix, and it’s a no-brainer. Coming from a guy whose sworn by shorties for the better part of a decade now, I wouldn’t touch a 5.56 less than 14.5” with a 10’ pole anymore. .300 truly hikes its leg up and trick ****s 5.56 in SBR applications.

Just do it, Will.

[WillBrink]

Given the discussion is regarding suppression, we’re dealing with polish blanket trick of barrel/suppressor.

A rebarrelling to .300 should set you back a whopping $150. .300 has become a lot more viable given the prices 5.56 has climbed to. Throw suppressors in the mix, and it’s a no-brainer. Coming from a guy whose sworn by shorties for the better part of a decade now, I wouldn’t touch a 5.56 less than 14.5” with a 10’ pole anymore. .300 truly hikes its leg up and trick ****s 5.56 in SBR applications.

Just do it, Will.

Rebarrelling is one issue of costs, it's feeding it that adds up real fast these days and availability another major issue to me. I don't like niche rnds, and narrowed my options to 9mm, 5.56, and 7.62., and the rest are all gone. I'm a pure pragmatist in the area. They may not be optimal in all situations, but have put more goblins down than any rnd and if you do your job, they will do theirs.

Having said that, you're 100% right that 300blk is the superior choice and probably get an upper in 300blk at some point depending on some variables.

[Outlander Systems]

If you’re married to the 7.5”, you could always train with the 5.56 and slap the .300 upper on when you tuck it into bed at night. Plink with the 5.56 and keep a small stash of .300 meat ammo around for solving problems.

Rebarrelling is one issue of costs, it's feeding it that adds up real fast these days and availability another major issue to me. I don't like niche rnds, and narrowed my options to 9mm, 5.56, and 7.62., and the rest are all gone. I'm a pure pragmatist in the area. They may not be optimal in all situations, but have put more goblins down than any rnd and if you do your job, they will do theirs.

Having said that, you're 100% right that 300blk is the superior choice and probably get an upper in 300blk at some point depending on some variables.

[WillBrink]

If you’re married to the 7.5”, you could always train with the 5.56 and slap the .300 upper on when you tuck it into bed at night. Plink with the 5.56 and keep a small stash of .300 meat ammo around for solving problems.

That is likely the future plan and best of all worlds...

Note: If/when we get "married" to anything, incapable of realizing/understanding that things change and evolve, we have failed hard. I see scientists, extremely smart scientists, MDs, etc who get "married" to their POV, and and no amount of evidence will change their minds. They suffer cognitive dissonance like anyone else and I don't find education has any impact there. We see that in the gun world, the audio world, etc, areas I travel quite a bit.

Having said that, I'm not an early adopter of anything, not a beta tester, will always default to vetted things vs latest greatest. But if/when evidence presents itself that it's time to adopt that evidence, I fail as an objective bases, science based, facts over feelz, person.

10 years ago, any mention of crazy a$$ shorty ARs would have gotten a no from me, for all the reasons you and others mentioned.

1911a is another one. I don't own any now, but it was an absolute rule anything below original specs was a no to reliability, and even officer length (4.25") was a no for some. Thus sayth the 1911 deities such as LAV, Bill Wilson, Hackathorn etc.

But, it appears that code was finally broken and according to LAV, via lots of effort from Bill W, legit reliable shorter compact 1911s now exist.

Same for 9mm 1911s. All of them I played with back in the day were Jam O matic garbage, not even suited for range toys, much less SD. Now it appears some excellent guns exist.

Audio: the rule, class D amps will never sound as good as class A or A/B, and to be ignored. That is now no longer the case.

On it goes for examples...

Chit evolves whether we like or not, and we either get with it and benefit, or we lose out.

[Outlander Systems]

That’s a good attitude to have. It took a (very long) while for me to warm up to .300 and in your application it’s absolutely the winning ticket.

[Todd.K]

I’m not trying to change your mind or argue. I get you are aware of the limitations and don’t disagree with your reasoning. For 5.56 I still recommend not going under 10.5” and I’ll list the reasons below for everyone else reading this thread.

The blast is huge. I know if it’s your life on the line you do what you have to do but I would hate to light off a round without earpro.

So now maybe it’s silencer time. But a mini silencer on a longer barrel ends up about the same for both sound and OAL.

I do not find anything besides concealment a shorter carbine than 10.5” brings in actual use. Even a 12.5” makes a super handy carbine.

Folding stocks change the concealment calculation for an AR.

The idea of an ultra small PDW is far more appealing than the reality of where most people will actually take it.

300BLK. Runs great, isn’t nearly as blasty, suppresses well and great terminal performance in the very short barrels. A great choice for an additional upper if you determine an actual need for something shorter than your 10.5” to 12.5” 5.56 carbine or pistol.

[WillBrink]

I’m not trying to change your mind or argue. I get you are aware of the limitations and don’t disagree with your reasoning. For 5.56 I still recommend not going under 10.5” and I’ll list the reasons below for everyone else reading this thread.

The blast is huge. I know if it’s your life on the line you do what you have to do but I would hate to light off a round without earpro.

So now maybe it’s silencer time. But a mini silencer on a longer barrel ends up about the same for both sound and OAL.

I do not find anything besides concealment a shorter carbine than 10.5” brings in actual use. Even a 12.5” makes a super handy carbine.

Folding stocks change the concealment calculation for an AR.

The idea of an ultra small PDW is far more appealing than the reality of where most people will actually take it.

300BLK. Runs great, isn’t nearly as blasty, suppresses well and great terminal performance in the very short barrels. A great choice for an additional upper if you determine an actual need for something shorter than your 10.5” to 12.5” 5.56 carbine or pistol.

In the end, 300blk is a better choice. That will happen at some point.

Of interest, SME level info on the topic via LF forums, and he does help fill in some gaps of understanding for me, supports some of what I'm saying in some respects, but does feel anything below 11.5 is a hobby gun vs a fighting gun:

"Everything is a compromise. 11.5" is generally the shortest barrel that doesn't result in too many negative results. As the barrel gets shorter, muzzle velocity and velocity at the target decrease. If you are depending on bullet fragmentation vs. expansion, you need to look at what you are asking the gun to do and at what range the velocity drops below the 2,500 fps (approx) threshold. No, I don't want to get shot with a bullet that just yaws, but then I don't want to get shot by anything. What I do want if I have to shoot someone is a bullet/gun combination that does as much damage as possible, thus increasing my odds to be the one that walks away without holes.

Going below 11.5" decreases the dwell time for a standard carbine length gas system, requiring a larger gas port with a resultant increase of hotter, higher pressure gas in the action and a faster unlocking. The bolt shouldn't unlock before the brass has had time to shrink away from the chamber walls. If it hasn't, then there is increased stress on the extractor and case rim. More heat, more stress means reduced reliability and longevity. This is accentuated as the barrel shortens and gas tube length is decreased. The entire gun's tolerance for gas, burn rate, bullet weight, etc. becomes less and less. That simply means ammo that runs in a longer gun may not run that 7" barrel.

There is a difference between a fighting gun and a fun/hobby gun. Yes, you may be able to adequately defend yourself with the latter. But if it fails at the range, minor or major, it doesn't matter. If you are using it for defense and it fails, the outcome is very different."

[Disciple]

"The bolt shouldn't unlock before the brass has had time to shrink away from the chamber walls. If it hasn't, then there is increased stress on the extractor and case rim."

The LMT enhanced carrier would reduce this problem as the unlocking is slightly delayed by the longer cam path. Have you considered running one in your 7.5" upper?

[WillBrink]

The LMT enhanced carrier would reduce this problem as the unlocking is slightly delayed by the longer cam path. Have you considered running one in your 7.5" upper?

I have not, but the gun has been dead reliable so far, but I have not put that many rnds through it as of yet. I'm not the least bit surprised such a gun runs hotter and likley reduce longevity. That makes perfect sense. You're forcing a gun to run on a rnd it's not optimized for, so something has to give no doubt. The barrel, as expected, gets silly hot real fast.