bjohnson_7, This is right from the Krieger website:
Q: What are the advantages of 5-R style rifling?
A: This is a tough one. There have been many reports and opinions on an "improvement" by using 5-R style rifling vs. conventional rifling. Many of these reports are of increased bullet speed, better gas seal on the bullet, less copper fouling/easier cleaning, etc. These are issues that are not prevelant with our traditional rifling style, so we really expect no improvement with our 5-R barrels. Our 5-R barrels are made with the same bore and groove dimensional tolerances and uniformity as our conventional record setting rifled barrels, so there certainly should not be a disadvantage. We offer the true Obermeyer style 5-R rifling in select calibers for shooters that feel there is an advantage to this style of rifling, you can be the judge.