Best barrel length for SBR, 10.5, 11.5, 12.5..?

[JCKnife]

I've read this and similar threads with interest, as I'm just starting my AR SBR build. I think I'm going to start at 10.5 but would also consider 11.5 if I find the 10.5 to be unreliable. I'm guessing the muzzle velocity difference between the two would be negligible.

[Zeus]

It's been my and other's experience that you will find 10.5's that run fine. However, you will find far more 11.5's that run "flawlessly" (figure of speech as ANY system can and will have stoppages).

[Travis B]

I think you need to back up a step and ask yourself a few basic questions, and once you've answered those questions your length issue will probably resolve itself.

1. Why do yo want an SBR?
2. What is the maximum distance at which you require you ammunition to perform as desired?
3. How Flexible is your ammunition selection (i.e. are you restricted to department or agency issued ammunition?)?
4. Do you intend to add a suppressor?
5. If so, do you know which suppressor you'll be adding?
6. If so, is it a QD suppressor with a mount and what mount is it?
7. etc.

Sorry to bump such an old thread, but I've been reading up on a lot of information for SBRs and I'm confused about suppressed vs. unsuppressed on a SBR. I plan on building a 10.5", 11.5" or 12.5" SBR and want to eventually have a QD suppressor for it (when funds allow). To address rob_s's questions:

I want the compact size of a SBR and feel the best way to go compact with an AR is to go with a SBR.

I don't forsee a need to go over 2-300yards with this rifle. (Is this within the effective range of a 10.5" barrel?)

I have no restrictions on my ammunition selection, other than civilian restrictions.

I plan to add a QD suppressor eventually. I don't know which suppressor I'll be running, or which mount it has.

From these responses, what do you recommend? Are there any threads I may have missed that specifically address the same concerns as mine? What are some of the best options for SBR suppressors?


Thanks!

[Magic_Salad0892]

Sorry to bump such an old thread, but I've been reading up on a lot of information for SBRs and I'm confused about suppressed vs. unsuppressed on a SBR. I plan on building a 10.5", 11.5" or 12.5" SBR and want to eventually have a QD suppressor for it (when funds allow). To address rob_s's questions:

I want the compact size of a SBR and feel the best way to go compact with an AR is to go with a SBR.

I don't forsee a need to go over 2-300yards with this rifle. (Is this within the effective range of a 10.5" barrel?)

I have no restrictions on my ammunition selection, other than civilian restrictions.

I plan to add a QD suppressor eventually. I don't know which suppressor I'll be running, or which mount it has.

From these responses, what do you recommend? Are there any threads I may have missed that specifically address the same concerns as mine? What are some of the best options for SBR suppressors?


Thanks!

I'm not Rob, but I'll bite.

300m is within usable range for a 10.5'' gun, not ideal, but you can use it.

I can take an 11.1'' to 600m, but admittedly haven't tried it with a 10.5'' gun.

I would recommend an 11.5'' over a 10.5'' due to additional frag range, and dwell time.

For suppressors, AAC, KAC, Ops Inc. and Surefire will be great.

[rob_s]

Most of this can be as much about the process as the answers. What you need to do is research and understand the limitations of whatever you choose. Unfortunately there is no SBR calculator where you input suppressor, ammo, max effective range required, etc. and it spits out the optimal barrel length.

One example of understanding limitations is suppressor mounting. A 12.5" barrel (ignoring handguard choice for a moment) will mount virtually any 5.56 suppressor on the market right now. Go down to an 11.5" barrel and you eliminate some of the reflex options such as the Advanced Armament SPR-M4 and (IIRC) some Ops, Inc. models. Go from 11.5" to 10.5" and you eliminate virtually all of the reflex options such as the Ops 15th model. At 10.5" you can mount almost any non-reflex can like the Advanced Armament M4-1000 and M4-2000 and the Gemtech Bi-lock mounts. Go to 10.3" or 10" and many of those cans won't fit either and you get limited to direct-thread cans at best.

Ammo selection is similar. As you reduce barrel length you reduce velocity which in turn reduces the "effective range". By "effective range" I mean the maximum distance at which the projectile will deform/fragment as designed. If you're shooting paper, this doesn't matter. If you're shooting "soft" targets, it may still not matter with good shot placement. And the variable changes based on the load selected. One of my eventual projects is to chrony a bunch of ammo from a bunch of barrel lengths and then begin to chart (surprise!) max effective ranges. But as of now I don't know of such a comprehensive resource in one location. Oh, and adding a can effectively adds barrel length with in turn increases velocity which therefore increases max effective range. All of which, again, matters not a whit on paper and steel.

FWIW, "I want the compact size" isn't really an answer. What matters is not "I want" but "I will use it for..." "I want the compact size for..." what? What purpose? What are you gaining when you lose those 5.5"? How does that impact your use? For example, I have one SBR for HD because I knew I was adding a can and wanted the package the same size as a 16" gun. I have another that I like for range use simply because it's small and light and stays out of my way when slung. Two COMPLETELY different reasons for "compact size". "I want" results in a situation where nobody else can advise you because it's all in your head anyway.

Finally, too many people "want" an AR to do all things all the time in all circumstances. What you wind up with is not something that does the best of everything but something that does everything half-assed. Figure out your primary intended role and design the gun around that, then learn to deal with the limitations. Everyone wants a 300 yard AR but nobody knows how to shoot at that distance.

[markm]

Holy necro bump. I didn't know that Pappabear had one of those pigs at one time!!!

[Travis B]

rob, thanks for the response. You're right, I should have been more specific in my hasty response. This rifle needs to be compact enough for a concealable bag (like the ones in the thread) but with enough barrel length to take care of wild animals that may end up on our chicken farm. I feel 11.5" has enough velocity to take down most prey within 200 yards (my shooting to 300 yards is without much experience, but I trust my 200 yard shots) and still fit inside a tennis bag, etc. When I first posted on this thread, I was still researching and was afraid to spend so much money on something that I would change later. But after even more research, I feel confident that a 11.5" barrel will fulfill my needs, suppressed or not. Now I just have to wait for my WillMaker software.

Thanks so much, everyone!