roaddog...I have found that very little is "absolute" in this game we love to play, so here are my thoughts on the Lee REAL.
The slower the twist, the "shorter" or "lighter" the Minie, or conical.
The faster the twist, the "longer" or "heavier" the Minie, or conical.
In the .54 with a 1:60 twist, I would suspect the smaller 300gr. to out perform the 380gr.
I also suspect that those "bad-mouthing" the REAL is because they have made the wrong decision on their selection.
Perhaps someone with more ballistic knowledge can give us a proper explanation as to why this will happen. I just know it does.
I shoot three different black powder calibers, in five different guns and this holds true in every case, Albeit, I have read, and talked to others, who did not agree with this. This is where I must ask myself, "what does shooting better" mean to each person doing the shooting. To me it is plain and simple;.....Better grouping with similar loads!
Good luck with your decision. Hope this helps.
Russ