Set screw for cam latch?
Doesn't sound like an SB2 frame to me, I wouldn't be sure that it's safe for modern loads, I'm not sure MSP knows what this rifle is, I've not seen one, but if it's the model I'm thinking of, it's definitely not safe for even levergun loads, but just trapdoor loads. What's the serial number on the frame? A call to H&R may answer your question as to what loads are safe. Just don't want ya to hurt yourself or the rifle, better to be safe than sorry. H&R's toll free number is below.
Tim
866-776-9292