Try going to www.milsupshooter.net Darrel has a scope mount designed for the M39 that works great. You do have to remove the rear leaf sight like the B-Square with his but it's make better than the B-Square and costs about $50.00. IMHO I don't think the Federal Arms unit is very good. I had one for a Mini-14 and it didn't hold up very well. Hope this helps.