Sadly, I'd have to agree - what you "just got" is actually some variety of Springfield .45-70, often called a "trapdoor" - not a .30-40 caliber Krag at all. Those all date from 1894-1904, and are an ENTIRELY different rifle.

You might want to try   (You need to Login, or, try the Trapdoor forum at   (You need to Login Either one should be able to help.

I can - and will - answer your questions, but it would be better done at either of those locations - and the former has a lot of info already posted.