It might be mounted with staking or soldering. A small product would be that the pin which retains the firing pin spring cap tended to work unfastened, and had to be tapped again in place as 1 noticed it challenge in the rear on the bolt. Winchester replaced that pin https://highimpactrounds.com/product/winchester-super-x-16-ga-2-75-in-6-1-oz-1165-fps-game-load-25-rd-box/