If I go with a 16" barrel will I be able to fit the PRI gas block flip up front sight? I've given up on the AE can so I'm not getting a collar. It will just be a smooth barrel with a brake.
Nope. You would need a low pro gas block. What are you are going to be building is pretty much a Mod H at this point. I don't see why the Ops Inc brake and collar setup would be hard to get....