old colonel,
In my considered opinion,you have made out like a fat rat.By your measurements,you will be able to use 45-70 cases,with little if any modifications,and 44 cal bullets.If you want to do so,you could trim the cases to 51.94mm, but it seems the other owner only trimmed enough to square the neck.The only good reason to trim further would be if it is necessary to seat some particular bullet.Commercial jacketed bullets intended for 444 Marlin should work very well with full length 45-70 cases. Cast bullets should be sized .430-.431",as long as they will go into a fired/unsized case(check .429" jacketed bullet also).For powder, we have been having good luck with 5744 in similar cartridges.Good luck. If you have any problems let us know.
Mike
