The "poorman's method" to EFFECTIVELY polish your chamber...
Start with a fired 3.5" shell
Drill out the primer
Drop a 2" long small dia bolt through the hole from the inside of the hull (bolt sticking out of the base of the shell)
Tighten a nut onto the bolt
Close the crimp of the hull
EVENLY wrap the hull in masking tape 2-3 layers thick (wrap the layers side by side, not overlapping, i.e. only spool it on perpendicularly, don't work up and down the length, add new wraps to get length)
If desired, coat the tape in polishing compound or jewelers rouge
Lock the bolt into an electric drill
Remove your barrel
Spin the hull in the chamber for a few minutes in the OPPOSITE rotation of how it's wrapped on the hull (otherwise it'll peel and roll up on you), working in and out of the chamber slightly.
That should help extraction.
If you feel that your chamber is "egg shaped", then you can try a new barrel, or try reaming your chamber by hand