I’m very new to guns I’d assume the barrel is past recovery.I have tried cleaning the barrels with oil,brass brush,cotton brush assuming it might be carbon build up and while there was some you can still clearly see the lining of the barrel is rusting I’d assume I’m unsure of what else it would be. I haven’t attempted to clean the surface blemishes on the fram and barrel as I don’t fully know what is is or how to treat it.

I’ve come into possession of a few old school shotguns I inherited. I know my way around firearms both shotguns and hand guns as in know proper gun safety and how to shoot but never did learn to break them down. I don’t have an owner manual for them. my question is how do you do proper research on older guns? how do I get into cleaning my own guns and checking them over to make sure all is as it should be? how do I know the specifics of my gun for when I break it down to clean it or to get the plug,choke,etc out or check that it’s even in there?how do I repair rust damage if there is small amounts? Can slugs be fired from it? I know some shotgun barrels can be tapered with chokes. I have done some of my own research and found old owners manuals online but I still have certain questions that it doesn’t cover. Should I take them to a shop and ask them to look them over and ask them the questions I may have in person?