it has been my experience that most american made guns have heavy enough barrel walls that opening chambers and forcing cones is safe...however, many light european guns made prior to ww1 have thin barrel walls and as such would be made unsafe by removing metal...best bet is to have all barrel work performed by professional gunsmith with tools and experience necessary to insure that gun remains safe to fire with modern ammo.
That's a good point ed. And a fair distinction between American and European guns...Geo
