Some time back, my father in law bought a sporterized rifle in 30-40 Krag for the scope that it was wearing and gave me the rifle... sweet!

I ran out and finally found some core-lokt ammo and eventually took it out to the range to find that I could not get it to group at 100yds. Same at 50 yds, etc. Did not bother to take pics of the targets due to the shame that I felt. But suffice it to say that I am capable of shooting 1/2 groups with some of my rifles.

Any tips that experienced shooters of this cartridge can offer to me? I've had me personal lessons learned on bullet stabilization and twist rate so I don't think that is my issue.