It could be fastened with staking or soldering. A little product would be that the pin which retains the firing pin spring cap tended to operate unfastened, and needed to be tapped again in place as one saw it project in the rear from the bolt. Winchester replaced that pin https://highimpactrounds.com/product/winchester-super-x-12-ga-2-75in-1-oz-8-lead-1290-fps-25-rd-box/