Barrel Length for a 5.56 SBR?

Discussion about 5.56mm ARs

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FormerNavy
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Barrel Length for a 5.56 SBR?

Post by FormerNavy »

I'm going to build a 5.56 SBR sometime in the near future. I've done a lot of reading up on barrel lengths. It seems anything under 10" starts to become finicky and have some reliability issues. I was originally going to go with a 10.5" but am now thinking maybe 11.5" or 12.5" for less wear and tear on my suppressor.

My basic desires are to use it with a suppressor, so I don't want to much wear and tear. Also, performance-wise I'd like it to be an effective round out to about 100-200yds with 55grn or 62grn standard ammo (read: maintain enough velocity to be effective out to about 100+ yds).

Am I on the right track here?
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300Blk
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Re: Barrel Length for a 5.56 SBR?

Post by 300Blk »

My 7.5 inch was perfectly reliable doing 100 round beta mag dumps.

I would go with 10.5. My 10.5 LMT was also reliable.

That all being said, that doesn't mean yours will be reliable. You have to know that the super secret to making them reliable is to use an H2 buffer, the proper gas port size, and the proper extractor spring (a Colt gold spring or an AAC spring and o-ring should be a good choice). This is the stuff that Colt never figured out in the 1970s.
FormerNavy
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Re: Barrel Length for a 5.56 SBR?

Post by FormerNavy »

300Blk wrote:My 7.5 inch was perfectly reliable doing 100 round beta mag dumps.

I would go with 10.5. My 10.5 LMT was also reliable.

That all being said, that doesn't mean yours will be reliable. You have to know that the super secret to making them reliable is to use an H2 buffer, the proper gas port size, and the proper extractor spring (a Colt gold spring or an AAC spring and o-ring should be a good choice). This is the stuff that Colt never figured out in the 1970s.

No concerns about increased pressure or wear and tear on a suppressor at the shorter lengths? What about ballistic performance out of the shorter barrel at ~100yds?
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300Blk
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Re: Barrel Length for a 5.56 SBR?

Post by 300Blk »

5.56mm is a bad choice for SBRs, but when someone makes a 5.56mm SBR, I assume they know that and just care about shooting cheaper ammo.

Yes, it wears down silencers faster and doesn't have good ballistics.

I would still do a 10.5 inch Mk18.
FormerNavy
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Re: Barrel Length for a 5.56 SBR?

Post by FormerNavy »

300Blk wrote:5.56mm is a bad choice for SBRs, but when someone makes a 5.56mm SBR, I assume they know that and just care about shooting cheaper ammo.

Yes, it wears down silencers faster and doesn't have good ballistics.

I would still do a 10.5 inch Mk18.

Yeah... but I have a 9" 300BLK... what else (if anything) would be a good SBR in a rifle caliber?
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Re: Barrel Length for a 5.56 SBR?

Post by 300Blk »

It won't be fully affective with 55 or 62 grain ammo past about 40-60 yards. 5.56mm becomes more effective with high-end ammo.

Maybe just 16 inch. AAC 16 inch 5.56mm uppers are fantastic. 40,000 rounds and zero malfunctions and it would match the AAC lower.
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Re: Barrel Length for a 5.56 SBR?

Post by BlackCloud762 »

Never had any issues from my PSA 10.5" other than I put a muzzle brake on it to serve as an extra/initial blast baffle, and without the can on it, it is painfully loud :o

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FormerNavy
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Re: Barrel Length for a 5.56 SBR?

Post by FormerNavy »

300Blk wrote:It won't be fully affective with 55 or 62 grain ammo past about 40-60 yards. 5.56mm becomes more effective with high-end ammo.

Maybe just 16 inch. AAC 16 inch 5.56mm uppers are fantastic. 40,000 rounds and zero malfunctions and it would match the AAC lower.
Yeah I have several full length ARs in 5.56... was just looking to build another SBR... maybe I should just build a second one in 300BLK if nothing else performs decently. :lol:
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Re: Barrel Length for a 5.56 SBR?

Post by 300Blk »

You could make a 9mm.
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Re: Barrel Length for a 5.56 SBR?

Post by IMGrunt »

FormerNavy wrote:I'm going to build a 5.56 SBR sometime in the near future. I've done a lot of reading up on barrel lengths. It seems anything under 10" starts to become finicky and have some reliability issues. I was originally going to go with a 10.5" but am now thinking maybe 11.5" or 12.5" for less wear and tear on my suppressor.

My basic desires are to use it with a suppressor, so I don't want to much wear and tear. Also, performance-wise I'd like it to be an effective round out to about 100-200yds with 55grn or 62grn standard ammo (read: maintain enough velocity to be effective out to about 100+ yds).

Am I on the right track here?
I'm in the process of doing the same and just taking my time on collecting all the components. I've done lots of reading from numerous sources and finally decided on 11.5. Pretty much, from what I've collected, the sweet spot for a 5.56 SBR without sacrificing too much on reliability, accuracy, and potential damage to a supressor. I'm sure others have their own opinions but that's my story and I'm sticking to it.
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