As usual, Tim is spot on, with Handi friendly scopes LO rings are the norm! I have quite a few H&Rs myself and almost all are scoped, I think two wear med rings, the rest haver LO!
Big objectives are not a huge problem, but with bull barrels may require med rings. Large variable adj knobs are the problem. as when coupled with the hammers on the H&R you need to go taller to get clearance.
The triming Tim is talking about is not awlays necessarry. Again of all mine maybe three have trimmed hammers. What we are talkning about is the 3/16" or so, that protrudes above the hammer spurr. (Once installed) You can grind or cut off with dremmel.
Leupolds, Nikons and many others fit just fine in LO rings.
CW