The early rolling blocks were case hardened.  There is a hardened layer on the surface that you go through pretty quickly when you mill them down.

The later models that were chambered in 7mm were heat treated instead of just pack hardened.

You can tell the difference easily by the size and shape of the receiver ring.  I can get you precise measurements when I'm at home, but as I recall, the shank on the smokeless powder heat treated ones is about 1.05 inches, and the earlier blackpowder is about .95.  The receiver ring is much thicker on the smokeless also.  The blackpowder actions have a kind of "step" on each side of the receiver ring where the ring gets smaller over the top of the action.

The only appropriate cartridges for any of these actions, including the 7mm smokeless action, is a blackpowder era cartridge, loaded to blackpowder pressures.  You can push this just a bit with the smokeless action, but it is in no way suitable for modern cartridges, unless very small (.25-20, .22 hornet, and possibly the .222).  Although it was designed for smokeless, the pressures were low and there were still problems with the action at that.  I've seen some in .32-40 and .30-30, and even a few in .308 and .30-06.  I personally would have no part of shooting any of these cartridges in a RB.

My recommendation if it is to be a hunting rifle would be .45-70, .45-90, .50-70 or .50 alaskan.  I have all of these cartridges in a RB, and they're excellent short range hunting cartridges.

I can help you identify the action you have later when I have more time to type, and I can help you get a good 3 pound trigger pull to replace the military 18 pound.

Best of luck,
dave