So, I am going to start a build this week.  I already have a Bushmaster M4, so I'm not new to AR's, just new to building them.  Going to pick up a CMMG lower and a parts kit, and I will add more parts as I have money for it.

Anyway, I'm under the impression that you cannot remove/install the FSB with a muzzle brake/flash hider on the barrel, and a 14.5" barrel must have the muzzle device permanently pinned in order to be legal.

Now, being in CT I cannot have a flash hider, I can only have a muzzle brake.  So, I'm thinking about ordering a 14.5" threaded barrel, and buying a muzzle brake, and having a smith pin it.

The problem is, I don't want to have a FSB on the gun, just a gas block with a flip up front site mounted to it, so if I ordered a barrel or upper with a pinned brake, I'm assuming I'll need to get that brake cut off first, which seems like a stupid idea.  

Unless that is I'm wrong and you can get the FSB off and a new gas block on without removing the brake.

What do you guys recommend I do?

You could order the barrel and brake you want already pinned/welded, then Cut the FSB off and replace with a clamp on flipup/gas block like YHM for example, a lot easier and way less likely to damage bbl.
You can order the whole deal done your way from some in the industry form also.

I didnt realize I cut cut it off and then use a clamp on one, thats a really good idea, thanks.

Thanks for the advice. I'm going to buy my lower tomorrow and will ask the store/gunsmith about getting me what I want and what the price would be.