It might be fastened with staking or soldering. A small item would be that the pin which retains the firing pin spring cap tended to operate loose, and needed to be tapped back in place as 1 observed it venture within the rear in the bolt. Winchester replaced that pin https://highimpactrounds.com/product/winchester-target-223-rem-55-gr-fmj-3240-fps-20-rd-box/