post ban to pre ban?

I own a 20 inch Bushmaster AR-15, post ban. Since the ban is ending(hopefully) I was told I can now legally conver the post ban rifle into a pre Ban rifle. Now if true what is the best way to do this...should I buy a whole new upper reciever, of can I somehow juat change the barrel, by just grab a pre ban barrel? Im sorry if this is a silly question, the guns new and I dont have much expierence on working on it.
Thanks

If you can live without the bayonet lug, you can have the barrel threaded for just a small fee, and then add the flash hider of your choice. If you must have the bayonet lug, then either a new upper or barrel changeout is in order. I have heard of people changing the front sight tower out for a new one with the lug, but sometimes with mixed results.

Good luck. I am going the thread route on my post bans.

Start threading!

WildweareAlaska

The gunsmith I know charges $100 to thread a barrel for a flash hider. When changing gas blocks, the trouble will be getting a new one that lines up just perfect with your barrel. You may have to get a new barrel and gas block that are matched. Save the $100 getting your existing barrel threaded, and buy a brand new barrel assemble with bayo lug for and $200.

Sheesh!! My local guy quoted $10 for "just threading" he said.