Polishing/Lapping a sticky AK chamber?

I posted about a problematic M70 Yugo AK a couple weeks ago in another section. Aside from some feeding issues, I am encountering stuck cases. They requir a few hard raps with a wood block to extract. I've tried 4 different loads, one being brass. Brass ammo had no issues, so it's not a "brass after steel" problem. The bore has visible circular milling marks and the spend cases have unusual and uneven marks. I would like to polish the bore up. What do you suggest?

As I am not a gunsmith, and not much of a AK guru, I don't intend to remove the barrel.

You should do a chamber casting and see what the inside of the chamber really looks like.
It may have some pitting that somebody already polished out and made an out of round chamber.
I have seen many surplus rifles with this condition.
Especially Mosin Nagants.
You can do your own Chamber cast with Cerosafe

If you have been shooting steel cases, you may have lacquer built up in the chamber.

I only ran about 20 rds of Golden Tiger, which is lacquered, but the previous owner ran nothing but Wolf Military, which is not. The chamber casting might be a good idea. Regardless, some sort of work is going to be required.

Chromed chamber and bore? If it's chromed you can't touch it without having the chrome stripped, hard as hell.
If it's unlined chromemoly the easiest thing to is take one of the steel cases fired in the rifle, drill out the primer sontou can attach a rod to it, smear the case with fine valve grinding compound, chuck it in a drill and spin the case at slow/medium speed in the chamber with light pressure, clean and check frequently. I have worked on a lot of former com bloc weapons that required this, keeps the chamber from going oval, but again go slow and thoroughly clean then test fire. The idea is to clean up the chamber and remove burrs and ridges, not make it super shiny, and don't move the shoulder forward or you will increase headspace.

Military barrel or a civilian manufactured?
Built from a kit or?