Chris in va, or anyone, what is bushing?
What is it's purpose?
Do you see the silver-colored part that surrounds the muzzle end of the barrel? That's a barrel bushing. It allows a tight fit around the barrel, supporting it and providing a bearing surface for it to slide along, without having to machine a perfectly-sized, perfectly-concentric opening in the end of the slide. Also, as the bushing wears over time and the fit gets "sloppy", the bushing can simply be replaced - there's no wear or damage to the end of the slide.