Can you make a pre-ban upper receiver legal for use on a post ban lower by removing the bayonet lug? I have a pre-ban upper with a muzzle brake (not a flash suppressor). What can I do to make it legal for use on a post ban lower receiver? I bought a pre-ban upper so that I could experiment with different muzzle brakes before I committed to a permanent attachment. I have the three hole y comp muzzle brake from bushmaster. I want to make it legal to attach to a post ban lower. help? Thanks.

Yup.  Two options here.

1. [b]Permanently[/b] attach the muzzle brake and cut off the bayo lug.

2. Trade your preban upper for a postban already set up with the brake you want.