I have shot thousands of .311 cast bullets through a .308 bore, no issues.

As far as an eroded chamber, that is a tough nut.

I would say leave the gun as is, and if you need to fire the gun, use a steel chamber insert to fire a hand loaded low pressure 32 H&R Mag round.

Mike

fun reading
https://www.chuckhawks.com/rifle_chamber_insert.htm