The heavier one (385 grains?) doesn't work out so hot in the 54 GPR, or at least in mine. I was able to manage 3-4" groups at 50 yards with the best possible combo, which was lubed felt wads and a hot charge of Goex 3f. But I had trouble keeping them on a 12x12" target paper by the time they reached 100 yards. It was as if they really started to wander as velocity dropped with range.
The shorter ones (can't remember the weight, and I'm not home to check) were better, but frankly not as tight as any number of RB loads at either 50 or 100 yards. Lubed felt wads and hot charges of Goex 3f rather than 2f seemed to be the key. I'm guessing that the combo of the hot charge for extra velocity, but also for better bullet upset along with the wads were at the heart of an accuracy system.
I kinda gave up on them because RBs were so much easier to cast, load and shoot. I'm not a long range shooter, but if that changes I'll certainly go back to the REAL again. But if I was serious about shooting conicals in my 54, I'd be changing to a Hunter barrel for the faster twist.