Well Treebeard, I've got a replica (Uberti) and 2 originals. One original I bought in '66 the other in about '93-5. The only problem I had was with the new (Uberti). They use the same magazine tube for .45 or 32-20. After you'd get about 6-7 shells in the tube it got harder to push in. They've got a kit out mainly for the .38 shooters, but I did basically the same thing, and this was before they had that kit out. I bought a 32-20 mag. tube, spring and follower. I measured it from the receiver to where the threads for the screw in cap ended inside the regular mag, centered it with thin pieces of wire, when I got it right, I pulled it out , cut it , scuffed the outside of the 32-20 mag. tube and the inside of the of the rifle's mag. with 60 grit paper. Washed them off with acetone. Put that modeling clay in the threads and in the mouth of the smaller tube , mixed up some Brownells Acra-Glass, slathered the smaller tube with it , pushed it in from the back while twisting it side to side to the top, right below the threads. Used the small pieces of wire to center it, wiped any excess off and let it dry overnight. I had to make a small bushing/adapter that stopped them from shooting on back through. Cleaned up everything. Works great now. I could have left it as is, but hey ,,,,,,,,,,,,, I'm like that. Mechanically wise, I haven't had any problems .
Have fun,
Isom