I mentioned .30-40 and not some other caliber (like 7.62X39 or .308 for example) because it is a rimmed case. If you look at a 7.62X54 while holding it next to a .30-40 Krag case, they look very similar...
This all started when my friend, who has both a Nagant and a Krag rifle, borrowed my brass tumber and put both cases in at the same time. We had a hard time sorting them when they were done tumbling because they look so much alike. That got me to thinking "hey dosen't anyone make a Nagant barrel in .30-40?" and then I posed the question to you guys. I don't have any plans to try this, I just thought it would be cool to do and was wondering if it were possible in case I wanted to try it latter...
Anyway, I think you could probably use the same bolt. My guess is that the only mod you'd need is a new barrel, but I'm not too sure about that. Any gunsmiths out there that have any thoughts on this?