It might be mounted with staking or soldering. A little merchandise is that the pin which retains the firing pin spring cap tended to operate loose, and needed to be tapped back in place as just one saw it job from your rear on the bolt. Winchester replaced that pin https://highimpactrounds.com/product/winchester-super-x-20-ga-2-75in-3-4-oz-rifled-hollow-point-slug-1600-fps-5-rd-box/