Best barrel length for suppressed AT 15 SBR

[oscar615]

As the title says, I want to build a AR15 SBR with a suppressor. Since I have to specify the length of the barrel up front on the form 1. Which length is the most functional? With ballistics, accuracy etc. 7, 10, 12? What are the opinions?

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[jjoker16]

I personally like the 10". Better ballistics than the 7" and most 556 cans are around 6". Making a total OAL of a 16" rifle.

 

[BlueHeaven]

It all depends on what you intend to use it for. Close quarters or distance (<100yards) / close quarters. I'd say the 7 & 10 would be close quarters only. You could maybe get some good distance with 12", but I've had experience with 14" good for both worlds, unless that's not what you want. Just my 2 cents.

 

[ABNsurveyor]

It all depends on the suppressor, one of my AR suppressors states that you can not use a barrel shorter then 10 inches, so I went with a Daniel Defense 10.3 inch from Midway USA.

 

[pwc001]

It is my understanding that you can not go shorter than what you have listed. You just must have the barrel the length listed and be able to put it back to those specs.

If you get a 7", then you can run any length longer than 7", but for me, I would not go shorter than 10", I just do not see any advantage.


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[ABNsurveyor]

If you get a 7", then you can run any length longer than 7", but for me, I would not go shorter than 10", I just do not see any advantage.

I have heard this a few times, but I would check with the ATF before changing the length of a SBR. If your weapon is X length and your Form 1 states Y length you are asking for trouble if LEO is looking for a reason to charge you with something.

 

[Lafsnguy]

You can change the length of a SBR as much as you want. You are only supposed to be able to return it to what you registered it in. If you wanted to make a permanent change you are supposed to notify the ATF and they will update their records. Either way it wouldn't be something you would get arrested for. Like everyone said I wouldn't go shorter than 10" but even then you lose a lot of velocity. Most manufacturers won't rate their cans for less than 10 inches. The Saker is the only one I know of rated for a 7 inch 5.56.

 

[eMGunslinger]

You also run into cyclic problems shorter than 10.5" if you plan on taking the suppressor off. Due to the decreased dwell time, you have to gas the rifle higher to get it to operate without a suppressor. When you put the suppressor on you run into over gassing problems which is annoying. 11.5" is the optimal length over 10.5" with just that extra 1" of barrel you make up 20% extra dwell time on the gas system. This is the most calm and best suppressed barrel option out there.

 

[JWG223]

You can change the length of a SBR as much as you want. You are only supposed to be able to return it to what you registered it in. If you wanted to make a permanent change you are supposed to notify the ATF and they will update their records. Either way it wouldn't be something you would get arrested for. Like everyone said I wouldn't go shorter than 10" but even then you lose a lot of velocity. Most manufacturers won't rate their cans for less than 10 inches. The Saker is the only one I know of rated for a 7 inch 5.56.

I want to say the AAC SD-N6 is rated to 8" on a 5.56. I would double-check, though.
I went round and round with this changing of uppers, as well. The NFA strongly REQUESTS that you notify them if you change the permanent configuration, but it is not mandatory. They request it for the purpose of keeping the registry current. If you were to ever sell the weapon, etc. is the only time it would be a hassle.