I'm looking to build a non-nfa other with a 11.5" barrel kit.  I have to pin weld the muzzle device on in order to make it legal length.   Since I can't swap it out, I want to make sure I get a good one (that's legal), but I don't know much about them.  Thanks.  

I know you could use a simple A2x flash hider, you might be able to use a standard A2, not 100% sure about that. 
 

There are tons of devices out there. Check SureFire as well, they may have something suitable for your purposes. 

Just fyi, if you use a VLTOR a5 extension tube, you meet the 26" minimum OAL without pinning with a 11.5" barrel.

Also, the Surefire SFMB556 is pretty sweet, the drawback being muzzle blast.

I think I would prefer a compensator or muzzle brake just to be on the safe side.  Flash hiders aren't legal in NJ on rifles and I want to be able to have options depending on what happens with the whole pistol brace issue.   

5 hours ago, ESB said:

Flash hiders aren't legal in NJ on rifles and I want to be able to have options depending on what happens with the whole pistol brace issue.   

You may prefer a comp/brake, but your reasoning is wrong.
• Flash hiders, in and of themselves, are legal in NJ. You can put a flash hider on a bolt gun, on a Mini-14, or a Fight Light SCR. They count as an “evil feature” - they are not outright illegal.
• If braces become illegal, remove the brace and run a bare receiver extension
• If you want to put a stock on it, you will have to rebarrel anyway as 11.5 = NFA

That being said, I recommend a Surefire WarComp.

Are you going for looks or performance or just getting something on there?

With a short 11.5" barrel, you're going to get a LOT of muzzle blast.  

I actually put on a Midwest Industries Flash Can on my 12.5" other - it directs a lot of the concussion and noise forward.

I have a PWS CQB comp on my 12" firearm. It does a fantastic job of sending noise and blast forward. As I f'd up and fired my firearm under an overhang without my electronic ear protection, it did a great job of keeping my eardrum from rupturing. 

https://www.primaryweapons.com/product-url-15922

I haven't used a war comp, but I'd like to try one. I have a BCM Comp  Mod 0 on my other "other", and that mofo is looooooouuuuuud. @High Exposure Have you used the Mod 0? I'm xurious how it compares to the Surefire.

19 minutes ago, ChrisJM981 said:

I have a PWS CQB comp on my 12" firearm. It does a fantastic job of sending noise and blast forward. As I f'd up and fired my firearm under an overhang without my electronic ear protection, it did a great job of keeping my eardrum from rupturing. 

https://www.primaryweapons.com/product-url-15922

I haven't used a war comp, but I'd like to try one. I have a BCM Comp  Mod 0 on my other "other", and that mofo is looooooouuuuuud. @High Exposure Have you used the Mod 0? I'm xurious how it compares to the Surefire.

Comps and brakes are very subjective.

I have a BCM Mod 1.5 on a 14.5” gun.

Warcomp is on a SBF.

I also have two SF MB556 and a SF Warden Blast Diffuser for the SF devices, a few PWS FSC556, a Battlecomp 1.5, and some Troy Medieval and Claymore Brakes. I also have access to A2s and Vortex flash hiders at work.

I never really noticed a difference in how loud they are. 

Also make sure you are comparing apples to apples. The same brake on a 16”, 14.5”, and 11” gun can feel/sound worlds apart. 

I haven’t noticed much of a difference from a shooters perspective. From a bystanders perspective, that’s a different story - The old school Bushmaster Y Brakes and the Lantac Dragon are obnoxious. 

I have a Battlecomp 1.5 on a 16" rifle. That is uncomfortable for the person next to you. PWS on a 12" SBF and the BCM Mod 0 on an 11.3" SBF.