It could have an easy fix. I found a couple of older threads that may be helpful using yahoo and google. I know there are more threads as I know I have contributed on at least a couple.
To help you it will be important to know what ammo, where the jam is happening. Is the feed stop installed and not buggered up.

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Forgot to say that is one nice looking Krag, if it is not original it needs to be nice looking, functional or something. You have got that covered, get the feeding fixed and that one will be alright.