am pretty sure who ever assembled my rife used a two liter bottle of red locktite.
first think i did was go to harbor freight and bought their cheapest heat gun and the biggest flat head screw driver they. Then I heated it up and let it cool back down for 30 minutes. i did that several times, since i assume locktite and steel would expand/contract differently when heated/cooled. After that i put the rifle in a vice (protected it with some rubber inserts on each side) and turned it ass hard as i possibly could. it is a real bitch but it is definitely possible.