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Old August 20, 2018, 12:53 PM   #1
HALL,AUSTIN
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10.3" or 12.5" 5.56 sbr?

Is there any difference in terminal performance using premium ammunition like mk262, 62 or 70 grain tsx, or gold dot soft points out to say 75 yards? I can't find any tests comparing the two barrel lengths. Also if you own or have shot both, is the 10.3/5 much more concussive/loud than the 12.5?

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Old August 20, 2018, 01:10 PM   #2
dallasb
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Quote:
Originally Posted by HALL,AUSTIN View Post
Is there any difference in terminal performance using premium ammunition like mk262, 62 or 70 grain tsx, or gold dot soft points out to say 75 yards? I can't find any tests comparing the two barrel lengths. Also if you own or have shot both, is the 10.3/5 much more concussive/loud than the 12.5?
Does this help?

https://rifleshooter.com/2015/12/223...s-to-6-inches/

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Old August 20, 2018, 01:12 PM   #3
Mobuck
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"is the 10.3/5 much more concussive/loud than the 12.5?"

At the level of muzzle blast produced, I don't think there's a noticeable difference.

Considering the velocity lost to the short barrel, terminal performance should be about what a normal length barrel would produce at 300 yards.
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Old August 20, 2018, 04:22 PM   #4
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The answer is easy.
In a 5.56 caliber AR, longer is better.

The ballistics of a 16.5 inch AR are identical to a 22" 222 Remington. So that's not too much of a drop.

And Yes--- the short barrels are VERY loud and if you look at the energy you get for that blast, it's not as powerful as a standard 218 Bee. However a 22 LR can be quite deadly, so I am not saying the effects of the SBR in 223 are to be laughed at, but I am not impressed with the concept at all.

I think many other rounds would be a better option. To my way of thinking, an SBR in 223 is mostly flash and noise, and you may be better off with a blow-back AR in 45 auto. At least a 45 auto can penetrate wall board a lot better, and is not near as loud, is very accurate at ranges out to 150 yards, and doesn't flash like a strobe light.
Not to mention the fact that the stoner system used in the 223 short barrels can be a tricky system to make work once the barrels gets real short. Not so a 9MM or a 45. Or for the gas system maybe a 300 Whisper. Or even the 7.62X39.

But the 223/5.56 NATO is an actual rifle round made form rifle length barrels.

To me the super SBRs in 223 are an example of the saying "Having lost sight of the objective, we'll redouble our efforts."

What is the purpose of an SBR? What's it's "mission statement"?

I thought it was for fighting, and for carry in confined spaces.
It's certainly not for target shooting or hunting.

So for carry in confined spaces the caliber doesn't matter at all.

But for fighting I would rather have a 45, a 40, a 9MM or a 7.62X39 long before I would consider a 223 with a 10" or shorter barrel. Sure, it will kill a bad-guy But so would a cut off 30-06 with a 9" barrel. So will a Ruger 10/22.

It's just that there are many better calibers to consider for the fulfillment of that mission statement when mated to an AR15.
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Old August 20, 2018, 04:42 PM   #5
HALL,AUSTIN
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I've got a 7.5" 300blk. Im making a trainer rifle in an affordable caliber, just wondering if it could possibly be more than a trainer.
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Old August 20, 2018, 09:20 PM   #6
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" just wondering if it could possibly be more than a trainer."

Somewhere in the 357 magnum category.
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Old August 20, 2018, 09:29 PM   #7
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I have a 7.5" 5.56 barrel. Since I am perfectly content with the velocities that I see (which are right in line with the link provided above), I'd also be more than happy about the velocities achieved in the longer barrels. As a reloader, I can also carefully select what bullet I am going to use, and can make sure the selected bullet will be appropriate for the calculated impact velocity.

I am also more of a fan of barrels at 9.5" to 10.5" than 12.5" (not that there's much difference), so I'd be quite happy at 10.5".

But, of course, some one shooting factory ammo might need to be a bit more picky.


Concussion won't be much different between 10.5" and 12.5".
I really don't think it's bad at all out of even a 7.5" barrel (nor does anyone that has shot mine or stood near someone firing it). Yes, it's worse than a 20" barrel, but still light-years from the blast that bystanders get from a .308 with a good break on it (let alone something like a .300 Wby).

Ah, heck... The blast and noise from my 10.5" 300 Blk are worse than the blast and noise from my 7.5" 5.56. Why? I don't know. Part of it may be the YHM 5C2 flash hider on the 5.56 redirecting a bit of it, while the .300 Blk has no muzzle device (unless suppressed). Or it may have something to do with the rate at which pressure builds behind the different projectiles (mass and bearing surface come to mind here). I really don't know, because predicted muzzle pressure for my go-to .223 load is five times that of my sub-sonic .300 Blk load, at those barrel lengths.
It's all subjective.

But I'm fairly confident in saying that you would have to spend a lot of time comparing side-by-side, before you'd be able to notice the difference in blast and noise between 10.5" and 12.5".
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Old August 21, 2018, 03:05 AM   #8
raimius
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If I had to do it again, I'd go with an 11.5in. That is about the maximum velocity loss I think is suitable for my kind of shooting (I usually use 55grn). It depends on use and ammo selection though.
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Old August 21, 2018, 07:53 AM   #9
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My 5.56 SBR is 10.5" and with a linear comp and good ear muffs, the noise isn't an issue for me. Before the rules changed I added a 5.56 silencer to my kit and it generally lives on the SBR, but I'm still not disappointed I didn't go shorter.

BTW, my .22 is 10" and my 9mm and .300AAC are both 10.5".. I like the way this barrel length handles for me.

Good luck
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Old August 21, 2018, 08:17 AM   #10
HALL,AUSTIN
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https://thenewsrep.com/85495/suppres...-5″-14-5″/

So I've found this. The jump from 11.5-12.5 was surprising.
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Old August 21, 2018, 12:22 PM   #11
T. O'Heir
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"...possibly be more than a trainer..." Any 10.3" or 12.5" 5.56 rifle is a big kid's toy. Big kid's need their toys too.
"...level of muzzle blast produced..." You would be able to tell anyway.
Ballistics by the Inch tested 45, 50 and 55 grain ammo. The difference is velocity, but not a lot. Couple hundred FPS at most.
http://www.ballisticsbytheinch.com/223rifle.html
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Old August 28, 2018, 11:23 AM   #12
daggertt
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did we already say to "get both?" That's what I usually end up doing.
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Old August 28, 2018, 02:35 PM   #13
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did we already say to "get both?" That's what I usually end up doing.
Or just buy an 11.5” upper and split the difference
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