What follows is what I have learned from some painful and expensive mistakes, ( and not a few stupid 'posts' here and elsewhere) I base my info on what I have found in research and from the good folks here and at the MSN site BPCR. As I want to shoot the "Target Classic" with only Black Powder my issues may be different. BUT
The 38-55 has a 1 in 18 twist and is rifled at about .3790 to .3795. The chamber will not take a bullet over .379 and what you really want in MHO is one at about .380 or even .381. So what to do? I have elected to have the chamber corrected. I wish I could change the twist to 1 in 15 but sadly that is not to be.
Others have elected to simply shoot soft bullets and maintain them at .375 to a max of .377. I want to shoot the 38-55 at distance longer than 200 yards and so I need a bulled that will cary. The rate of twist limits me to .270 tops and now the challange is to have a mold made to attain a round nose bullet at .270, More on this later.
As for the rifle, it is a beautiful rifle, great fit, trigger is sweet and after that 45-70 you will really love the limited recoil of the 38-55.