I have a 38-55 that I wanted to throat out just a little to add more blackpowder. I got a new reamer/throater that measured .379, I installed it in the chamber with some cutting oil and gave it a couple turns. I measured the progress, none. So I put a little bit of pressure on the cutter and I really moved. I panicked and checked the progress. OH NO, the dam thing cut a .60 inch throat. It WAS a new barrel until then.
I thought that I was really screwed until I shot the thing, it didn't seem to loose any accuracy.
Did I luck out or am I going to have trouble and it was just luck the I shot a half desent group. I keep saying to myself, boy have you done it now. I haven't dared tell any one to the date. Help, what shall I do?

That isn't to much freebore for that caliber to use longer bullets or set regular bullets out.And it will definitely help to run heaviest loads.My 458 long wildcat I used .8 freebore, and works fine even with 9000 ft lb loads.
Pour the powder to her and have fun.Ed

Breach seat the bullets. This will keep you busy and it may shoot even better.

Check on some Schuetzen sites to see how they do it.