5.56 out of 10.75" AR

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CCIman
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5.56 out of 10.75" AR

Post by CCIman »

Considering a SBR AR with a 10.75" barrel.

How ineffective is this as a defensive weapon when using factory ammo?
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Re: 5.56 out of 10.75" AR

Post by ArmedAviator »

For an SBR, I'd use Mk318 Mod 0. It will definitely be harder to find than M193 or M855, but if you can find it and keep a few magazines handy, that'd be my preference.
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Re: 5.56 out of 10.75" AR

Post by TSiWRX »

CCIman wrote:Considering a SBR AR with a 10.75" barrel.

How ineffective is this as a defensive weapon when using factory ammo?
What's not to like? 28-30 rounds in a pretty darned compact and lightweight package with very easy to manage recoil that should easily out-do a pistol when it comes to accuracy-at-range.

What am I missing? <--- that's an honest question.
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Re: 5.56 out of 10.75" AR

Post by ArmedAviator »

TSiWRX wrote:
CCIman wrote:Considering a SBR AR with a 10.75" barrel.

How ineffective is this as a defensive weapon when using factory ammo?
What's not to like? 28-30 rounds in a pretty darned compact and lightweight package with very easy to manage recoil that should easily out-do a pistol when it comes to accuracy-at-range.

What am I missing? <--- that's an honest question.
This is a good point. I guess I did not answer your question. It depends on the bullet how inneffective/effective it is. At medium to long range, M193 or M855 will not be as effective due to the lower velocities required for fragmentation. If you use a heavier bullet designed to expand instead of fragment, you will have satisfactory results. Mk 318 Mod 0 ammunition has a good track record with the special forces soldiers using SBRs.
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Re: 5.56 out of 10.75" AR

Post by CCIman »

Certainly tacti cool to want one, and you can put nice holes on paper at 200 yrds...but:

As you get to shorter barrels, the terminal impact bullet velocity affects the "effectiveness" of the bullet construction's behavior (fragmentation or expansion- vs punching 22 size holes) on target. There is debate (my question) whether civilian use of SBR in 5.56 under 12" barrel is actually LESS effective than handgun rounds for stopping power.

I Did not know about MK318-- how do you buy these? Does Hornady TAP or Z-max come close?
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Re: 5.56 out of 10.75" AR

Post by TSiWRX »

^ Ah, I see, gentlemen. Thank you for the education. 8) :D That indeed does answer my question!
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Re: 5.56 out of 10.75" AR

Post by pleasantguywhopacks »

Isn't the current thought that 14.5" is just about as short as one wants to go? My TC contender does well at 14".
http://www.youtube.com/watch?v=qOxXpNBdrVE" onclick="window.open(this.href);return false;
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Re: 5.56 out of 10.75" AR

Post by ArmedAviator »

If you're going to reload anyway, and you have some money to put into it, get it in .300 AAC Blackout. It's terminal ballistics look quite a bit better than 5.56x45 even out of an SBR.
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Re: 5.56 out of 10.75" AR

Post by CCIman »

I'm actually debating whether to do it at all-- SBR a AR that is. I asked the question here because, I have no intention of handloading, but you guys know the snizzle on ammo choice.

I currently am running a PWS AR with a 14.5" barrel weld-pin extended to legal 16"-- very kick butt. I've seen and held the TAVOR, and it is very compact and space efficient with a full 16" barrel- but a little heavy and chunky.

I thought hmmm....I can get about the same dimensions with a 7.75" PWS (or slightly longer 10.5"), and weighs also 2 pounds less. BUT, the fine details come into play: Accuracy beyond 200 yards and terminal effectiveness at any range using a 10.5" or smaller 1:7 barrel affects whether to even do it at all-- and just pull the Glock. OR am I over anal-yzing this??
ArmedAviator wrote:If you're going to reload anyway, and you have some money to put into it, get it in .300 AAC Blackout. It's terminal ballistics look quite a bit better than 5.56x45 even out of an SBR.
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Re: 5.56 out of 10.75" AR

Post by Morne »

CCIman wrote:I'm actually debating whether to do it at all-- SBR a AR that is. I asked the question here because, I have no intention of handloading, but you guys know the snizzle on ammo choice.

I currently am running a PWS AR with a 14.5" barrel weld-pin extended to legal 16"-- very kick butt. I've seen and held the TAVOR, and it is very compact and space efficient with a full 16" barrel- but a little heavy and chunky.

I thought hmmm....I can get about the same dimensions with a 7.75" PWS (or slightly longer 10.5"), and weighs also 2 pounds less. BUT, the fine details come into play: Accuracy beyond 200 yards and terminal effectiveness at any range using a 10.5" or smaller 1:7 barrel affects whether to even do it at all-- and just pull the Glock. OR am I over anal-yzing this??
ArmedAviator wrote:If you're going to reload anyway, and you have some money to put into it, get it in .300 AAC Blackout. It's terminal ballistics look quite a bit better than 5.56x45 even out of an SBR.
The .300 AAC Blackout is ideal, especially with barrels shorter than 10 inches. Longer than 10 inches and the 5.56 still has validity but not as far out as from a full carbine barrel. Figure that you won't get fragmentation beyond 100 yards unless you use a dedicated varmint load like the Black Hills Barnes TSX .
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Re: 5.56 out of 10.75" AR

Post by Ring »

pleasantguywhopacks wrote:Isn't the current thought that 14.5" is just about as short as one wants to go? My TC contender does well at 14".

if you shooting at someone at 400y... but thats not the point of a defencive SBR... shots would be PB to 50y max?... a 10.5 with good ammo, will decimate at that distance...
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Re: 5.56 out of 10.75" AR

Post by pleasantguywhopacks »

Ring wrote:
pleasantguywhopacks wrote:Isn't the current thought that 14.5" is just about as short as one wants to go? My TC contender does well at 14".

if you shooting at someone at 400y... but thats not the point of a defencive SBR... shots would be PB to 50y max?... a 10.5 with good ammo, will decimate at that distance...
I would like to see some testing data on that..
http://www.youtube.com/watch?v=qOxXpNBdrVE" onclick="window.open(this.href);return false;
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Re: 5.56 out of 10.75" AR

Post by Ring »

pleasantguywhopacks wrote:
Ring wrote:
pleasantguywhopacks wrote:Isn't the current thought that 14.5" is just about as short as one wants to go? My TC contender does well at 14".

if you shooting at someone at 400y... but thats not the point of a defencive SBR... shots would be PB to 50y max?... a 10.5 with good ammo, will decimate at that distance...
I would like to see some testing data on that..

10.5" SBR

Win. 5.56 Q3131 55gr.
90 rounds fired:
Hi Vel: 2959
Low Vel: 2749
Average Vel: 2840

Black Hills 75 Gr. Match HP
25 rounds fired:
Hi Vel: 2405
Low Vel: 2322
Avg Vel: 2362

PMC 55 Gr. FMJBT
20 rounds fired (one box)
Hi Vel: 2554
Low Vel: 2426
Avg Vel: 2514

S.W.A.T. mag. (nov.09), on page 74 they tested troy's M7A1 7.5" barrel, it pierced the Safariland level III vest at 50 yards.

and since this is for defensive use, you should be using Soft point or hollow point or BT tipped rounds, whereas the military is restricted to FMJ rounds.
and only the FMJ's will have spotty frag issues at those low speeds... not any of the expanding ammo.

http://pistol-forum.com/showthread.php? ... Duty-Loads" onclick="window.open(this.href);return false;
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