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Preferred 5.56 SBR length

Best 5.56 SBR Length?

  • 10.3/5

    Votes: 19 29.7%

  • 11.5

    Votes: 30 46.9%

  • 12.5

    Votes: 15 23.4%
  • Total voters
    64
MGnoob said:
…

If you’re gonna go short for the purpose of going short. 7.5” the way to go… Perfectly accurate out to 200 yds
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Why, just why? Range novelty? You can get the same energy from a 9mm that short, which much much less blast. Nevermind 300blk options.
 
PappyM3 said:
Why, just why? Range novelty? You can get the same energy from a 9mm that short, which much much less blast. Nevermind 300blk options.
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I never said .223..SBRs are gay without a can.
 
If you want a SBR'd lower for future use with something worth being short, then get whatever you like.

12.5 is the current hype beast consoooooooom trend, but in truth at 12.5 you may as well spend the $200 on a brake and pin/weld job on a 13.something" barrel and not bother with the feds.

I thought a 12.5 would be cool, so I chopped my MCX barrel to 12.5 and wish I cut it to 10 on the dot because that is what my can is rated for. Next time I am over at PMM I am probably going to ask if they will cut it down again.
 
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edmorseiii said:
…

12.5 is the current hype beast consoooooooom trend,
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Is 12.5 the new thing again?

edmorseiii said:
but in truth at 12.5 you may as well spend the $200 on a brake and pin/weld job on a 13.something" barrel and not bother with the feds.

…
Click to expand...
Kind of agree, if one wants one of the long boy open tine flash hiders. But a 12.5” with an A2 bird cage is still a good deal shorter than a 13.7/9 P&Wed to 16. ~2.5”
 
PappyM3 said:
Is 12.5 the new thing again?


Kind of agree, if one wants one of the long boy open tine flash hiders. But a 12.5” with an A2 bird cage is still a good deal shorter than a 13.7/9 P&Wed to 16. ~2.5”
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Yeah, I get it, but at what point in the real world is that ~2" worth it? That length and weight savings doesn't warrant the fed paperwork associated with an SBR and if you are chasing velocity numbers, a short barreled 556 isn't what you should be looking at.

Now if homeboy wants a 7" 300blk and a 4" 22lr upper, and the 556 upper is a holdover to get there? Sure, then it would be worth it in my eyes.

If there was no fed stamps and/or the pistol thing was an option, I would be all about a 12.5" with a dot/magnifier setup.
 
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edmorseiii said:
Yeah, I get it, but at what point in the real world is that ~2" worth it? That length and weight savings doesn't warrant the fed paperwork associated with an SBR and if you are chasing velocity numbers, a short barreled 556 isn't what you should be looking at.

Now if homeboy wants a 7" 300blk and a 4" 22lr upper, and the 556 upper is a holdover to get there? Sure, then it would be worth it in my eyes.

Now if there was no fed stamps and/or the pistol thing was an option, I would be all about a 12.5" with a dot/magnifier setup.
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What about an 11.5” with a warcomp? Is that with the tax stamp? It’s about the same length as a 12.5 with a bird cage.

It really boils down to whether someone wants to go through the SBR process. Yes, a P&W AR could be the only AR someone “needs”. But the SBR is still better in certain circumstances and the few inches shorter does make a difference, especially in older New England homes.

I do think that if the NFA weren’t a thing then the 12.5 would become more popular as a “one rifle” length for people who aren’t into buying multiple ARs or multiple uppers.
 
Is this a thread about best all-around barrel length or best SBR length?

If I could only have one AR rifle, it’d be a 14.5”. But if you’re building an SBR to put on a bench and shoot with a 10x optic, you’re doing it wrong.

Smaller is better, as I like to tell the girls.
 
doctorbossman said:
I think an 11.5" barrel will give 55gr fragmentation velocity out to 100 yards.
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You’ll be in the ~50% chance of fragmentation with M193 at that range. Even at the muzzle, 10.5s and 11.5s don’t provide enough velocity for consistent fragmentation with M193. I put this together with old Army terminal ballistics testing, averaged muzzle velocity data, and a ballistics calculator. M193 just doesn’t have great terminal ballistics range no matter what you’re shooting it with. When you start looking at modern bullets like solid copper TSX and 77gr TMK, the effective terminal ballistics in SBRs starts getting pretty far out there.

3407A624-EA6E-4D01-AD65-0B79A5FCC20B.jpeg
 
PappyM3 said:
You’ll be in the ~50% chance of fragmentation with M193 at that range. Even at the muzzle, 10.5s and 11.5s don’t provide enough velocity for consistent fragmentation with M193. I put this together with old Army terminal ballistics testing, averaged muzzle velocity data, and a ballistics calculator. M193 just doesn’t have great terminal ballistics range no matter what you’re shooting it with. When you start looking at modern bullets like solid copper TSX and 77gr TMK, the effective terminal ballistics in SBRs starts getting pretty far out there.

View attachment 692071
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Great info.
XM193 is what I have in bulk, so I guess I'll be taking a few steps towards my target to get reliable fragmentation. I'll need covering fire [mg]while I bound forward.[cheers]
 
OJ didnt do it said:
I would love a BCM 11.5 with a pinned FSB but they seem to be sold out on all the common places. Great looking setups man.
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If it is 11.5" you want, then get the Colt Commando upper. Add muzzle device of your choosing.

For range fun, get the 10.5" or 7.5". SBRs are not for long range accuracy nor for velocity so as far as I am concerned all that discussion is nonsense. Not too mention who here is engaging threats out to 100 yds anyway? You aren't hunting with an SBR.

Here is me with 7.5" barrel and 'special' ammo:

Steve M16 Blast2 crop.jpeg
 
doctorbossman said:
Great info.
XM193 is what I have in bulk, so I guess I'll be taking a few steps towards my target to get reliable fragmentation. I'll need covering fire [mg]while I bound forward.[cheers]
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Just remember, a .223 hole in the vitals, particularly the central nervous system, will still stop a threat. Doesn’t matter if that .223 is fragmenting or ice picking through. It also just so happens to be that the closer ranges are when you need fragmentation more for more immediate threats. The farther away they are, the more likely a non-life threatening hit will make them disengage and bug out.

That said, we have a lot of ammunition options as civilians and I think it is worthwhile to start saving up at least a combat load of ammunition with quality external and terminal ballistics. And make not of what zero offset you need to dial if you run out of those and go back to your bulk M193.
 
PappyM3 said:
What about an 11.5” with a warcomp? Is that with the tax stamp? It’s about the same length as a 12.5 with a bird cage.
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To me? No, it becomes a diminishing returns to me in light of NFA requirements. The reason I put a short (10.5") AR15 together in the first place was because I had finally bought a 762-SDN-6 10 years ago and that thing is a PIG, so going short meant going as short as still useful to balance out the length and weight of my can. Today cans are lighter and shorter, so I probably wouldn't go short on 556 gun again. I have grown to love my 14.5" gun with SF SOCOM2, but I also have a 6'4" wingspan.

Now other calibers? 300blk is why I bought a MCX and SBR'd it.

I am probably going to be a complete hypocrite some day soon and SBR a lower to build a MK18 Mod 0 out of wall hanger sentimentalism, but that is a completely different justification.
 
67ray said:
For range fun, get the 10.5" or 7.5". SBRs are not for long range accuracy nor for velocity so as far as I am concerned all that discussion is nonsense.
Click to expand...
7.5” is purely for PDW/vehicle operations. But 10.5”+ can go farther and have been proven out to several hundred meters. Not long range, but enough range to be worth discussing.

Hell, my 12.5” shoots 77gr TMK at 3/4 MOA, with reliable fragmentation out past 300 yards. And at 600 yards, it would have 25% less wind drift than a 20” shooting M193. Today’s SBR length capability is not what it was in the 20th century.

67ray said:
Not too mention who here is engaging threats out to 100 yds anyway? You aren't hunting with an SBR.
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Not in MA, but lots of people hunt with SBRs.
 
I was heavily considering something in the 11"-12.5" range as there's plenty of reasonable arguments for those lengths. Ultimately I decided on 10.5" as I already have a couple 14.5" P/W and if I was going to bother with the tax stamp I wanted the SBR to be noticeably shorter, lighter and more maneuverable. So far so good. Easily rings the gong at 100 yards and that's good enough for me. Here's my daughter enjoying it… 😁

IMG_2297.jpg
 
OJ didnt do it said:
What brand/model is your 12.5? I’m very partial to the pinned FSB
Click to expand...

It's a total Frankenbuild that was never supposed to end up as my favorite upper lol.

Spikes Industries complete upper
DS Arms BCG
milspec charging handle
Blackhole Weaponry/Crusader Arms barrel
DoubleStar CAR15 skinny handguards
Surefire SFCT (closed-tine) flash hider
Completed with Surefire FSB flashlight mount with Solarforce flashlight (single body battery) with Surefire UM00 tailcap and ST07 switch.
 
My 10.5" upper is plenty accurate out to 120 yards (max distance at my range unfortunately). I wanted a SBR so I could have a lightweight compact rifle for offhand shooting at the range. It fits the bill nicely. I didn’t build it to do benchrest shooting with a giant scope on it. To each their own
 
PappyM3 said:
This whole thread is about 5.56.

SBRs without cans are still awesome. A lot lighter and handier than with a can.
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Lol your right sorry.. I got past the title of the thread and got caught up on the op wasn’t necessarily against 300 blackout ect.

I still stand by my statement though about their length.. Without an intended purpose.

I wouldn’t go any longer than 10.5 if you’re doing an SBR
 
MGnoob said:
Lol your right sorry.. I got past the title of the thread and got caught up on the op wasn’t necessarily against 300 blackout ect.

I still stand by my statement though about their length.. Without an intended purpose.

I wouldn’t go any longer than 10.5 if you’re doing an SBR
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😄 We can all get a little caught up when talking fun guns.

And yeah, we all have preferences. I get why people wouldn’t want to bother with an SBR longer than a certain length.
 
I have owned and tried a number of different length uppers on my registered SBRs, DDM4 MK18, DDM4 300S, Colt MK18 and Commando 11.5, KAC CQB 11.5, HK 416 10.4-11, LMT MRP DI (Specwar) with a 12.5 barrel and MRP piston with 12” barrels. They’re all different. If running shorter unsuppressed, and DI, go with a 11.5 to 12.5. If running unsuppressed and piston, go with 10.5-12. The main criteria are reliability and gas. DI, the extra dwell time goes a long way, plus less gas back in your face (bigger issue with suppressor). If piston, you reduce gas quite a bit, and reliability over gas is significant. I’ve never had a hiccup with my piston uppers. My favorite setup at the moment is an LMT MARS with a piston MRP upper and 12” barrel. Its super pleasant to shoot, feels like its underpowered but isn’t. No recoil. Its very accurate to 150 yards. Its not that loud, and you don‘t get gas back in your face. LMT uppers are modular so its stupid easy to swap barrels if you decide to go different lengths or gas systems, or different setups.
 
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