It may be mounted with staking or soldering. A little item would be that the pin which retains the firing pin spring cap tended to operate loose, and needed to be tapped again in place as 1 noticed it challenge from your rear with the bolt. Winchester replaced that pin https://highimpactrounds.com/product/aguila-308-win-150-gr-fmjbt-2750-fps-20-rd-box/