5R Rifling!

[grayfox]

The advantage I've seen marketed is that the rifling does not directly oppose another rifling ridge, rather it is opposite a groove, which is supposed to cause less deformation and friction within the barrel as the bullet travels down the pipe. I can see where that could be true. OTOH, one match barrel maker has told me that neither they, nor any of their shooters, see any performance difference btw 5R and 4R. Personally I kind of like the 5R style but not really sure how true the benefit is...
Some 5R's are also "polygonal" which means potentially even less bullet-mating friction...
Barrel "goodness" IMO is probably more a function of the mfr, the steel, and their processes/QA, than the specific rifling style used.