Ideally you should trim the excess barrel length and recrown... Which couldn't hurt.
But the easiest route is two crush washers. I don't care for peel washers.
Yeah, I'm not uhm "trimming" barrel.
Crush washers.. thats what I'm using. The ones in the link you sent me..
These guys.. http://store.carolinashooterssupply.com/servlet/-strse-832/M14x1-TPI-7.62-AK47/Detail
I'm just going to take two of those, and invert them and that would do it.