Lee Loader

Why do some data tables write this bullet designation two different ways? Or am I missing something and there is actually a difference between RNFP and LRNFP? It's confusing, like when Hogdon used to call its Universal powder Universal Clays.

Can't speak to the Clays , Universal , Universal Clays thing .
The RNFP/LRNFP is a tool to distinguish between a cast or swaged bullet and a plated , half jacket , TMJ or FMJ . Many times there isn't data for a specific cast bullet , Lyman has moulds in circulation with the same number that have added , dropped , changed shape and length nevermind completely gone to a whole different bullet . That can alter pressure , oal , weight etc . The "L" is just making it clear that the data is for a lead bullet naked and lubed . That data may even be reduced loads for a swaged hollow based bullet in the original data .

Thousands of details , 100 that really matter , 10 make a difference to the casual shooter .
Work within the start low work up in 10 steps from the highest minimum to the lowest max in 3-10 written references and you'll likely never get hurt and find a 5-10 shot inside a quarter to a half dollar every time .