Can you have a threaded barrel on an ar-15 legally in NJ? I want to order a upper receiver and the company can't permanently attach a muzzle brake for me. Was thinking of buying the upper with a threaded barrel and having someone in Jersey permanently attach it for me.

Technically yes. However, there is the 'constructive possession' issue that someone who is more familiar with the laws can speak more about. Generally, if you possess the parts to assemble a working firearm (lower, upper, etc.), then it can be considered constructive possession and would be illegal as you would have an "assault rifle." But again, I stress that someone else more familiar with the legal aspect speak up-- I just wanted to address the question in the short term.

 

ETA: To clarify and expand on my initial answer... if you have just the upper with the threaded barrel, then that would be considered to be OK (from my understanding, but don't take that as the definitive truth).

Have it shipped directly to a FFL dealer you have made arrangements with that will attach the brake/comp and then pin it for you. This is one approved method. Two forum sponsors, Mastodon (Highland Lakes, NJ) and Arms-N-Ammo (waterford works, NJ) are capable of performing this service.

Adco Firearms in Ohio can pin it for you also and then ship it direct to you. Look under shop services.

I had ADCO do my brake work a long time ago. However, had I known better, I would have contacted one of our vendors (as T Bill noted)-- not only because they're vendors and you'd be supporting local business and interests, but because their work is vetted by numerous users on the forum and beyond.

Thanks everyone, I have to go to mastadon to pick up my zed lower. I'll talk to the guys when I go there and Definetley agree with supporting NJ companies.