i have a Rob Roberts 655 that patterned well with both the 3.5" LB 5's and 6's. i chose the 6's and had good luck with them this year. i can't remember the pellet count at the 40-yard pattern board, but i have it on my phone at work. i'll check it tomorrow and let you know.
what i like is the RR choke protrudes from the barrel about one inch at most, unlike some of the others. maybe a personal preference, but i like the shorter tube (as long as it patterns well)