Here's what I had to deal with recently. Not to diss the previous owner, not even for a second! But simply to show what corrosive ammo can do. Gun was cleaned after shooting, but chamber was probably not flushed properly with hot water, and not oiled / greased for long term storage (2 years, give or take).
After using de-rusting solution and a regular bronze brush, chamber still shows pitting, and is oversize (unfired round does wiggle in there).
If anyone says corrosive ammo is a myth...
The rifle I am talking about has rusted barrel also.
Just shoot it...