The guy that made the barrel is making me a new one. The spacer will work if it is not threaded. Already tried my ar spacer for 1/2 x 36. Did not work. However the crush washer may work. Tried it and it appeared to work. Going to check with liberty tomorrow though.
If you are talking about using a crush washer in place of a spacer, do not do it. You can not guarantee it will be perfectly even all the way around, and if you have any type of cant, you could have a baffle strike.