It may be set with staking or soldering. A small item is that the pin which retains the firing pin spring cap tended to work loose, and needed to be tapped again in place as one noticed it task with the rear of your bolt. Winchester replaced that pin in https://highimpactrounds.com/product/winchester-super-x-12ga-2-75in-1oz-6-lead-shot-1290fps-25-rd-bx/