RF is not one of my bullet designations, but comes from Lee I believe and I think I've seen it on several other manufactures products. It stands for round flatnose, which means a rounded ogive and flat nose of coarse, . which can mean anything so far as size of the flat. But size of the flat should mean everything, not the reverse.
The LBT FN (for calibers from 35 down) is a specific sized meplat, which is .090 smaller than bullet diameter. Any caliber over using the same profile I, for some unknown reason 27 years ago, called a WFN, but specs are the same. The WLN has the same meplate but a much longer ogive, and I never recommend it for lever action rifles. The FN or WFN can be seated deep enough to chamber in about any lever rifle, but it sometimes takes a bit of care closing the action. The LFN on the other hand, has a meplat .125 smaller than bullet diameter and feeds in about any lever or bolt rifle around. It's meplat is large enough to get into the ideal kill zone DV of 125 with most rifle cartridges and revolver cartridges in rifles if caliber is over 35. Max DV or optimum kill speed is 130 and an expanded 35 bullet goes WAY over that, so don't let any softnose bullet lock your mind into thinking a hard cast, NON EXPANDING bullet with adequate meplat and impact velocity is not completely adequate on big bears ans such. I would chase the biggest brown bear in a heartbeat with a 35 rem loaded with an LBT LFN moving out at 1900 fps or so. Any weight from 180 gr up would make me comfortable, but I'd prefer 200 gr or a bit over for better accuracy.
Sandpoint is just 26 miles over the hill from my place and I can see almost half of the distence, across grizzly bear country, which comes right up to my back yard. One tried to open a neighbors screen door a few years ago, but couldn't figgure out how to swing it and didn't think to just take it off, so it wandered away. On second thought, he may have seen the woman witch inside which would definitely send anything with an IQ over 10 in search of better company. Not that I don't like her, and everything. The point being I live with grizzleys, ---------- and only a mile from her, so I think I know what it means to keep enough gun handy.