.There is some interesting reading on Boots Obermeyer's site on barrels and rifling. Boots is a one man shop for barrels and is getting on in years but the man probably knows more about barrels than any man alive. Bartlein Brux and others have gone to Boots to learn the trade. The quote below is from his website questions and answers. http://www.obermeyerbarrels.com/
Boots is the man that developed 5R rifling
Boots is the man that developed 5R rifling
Quote:What does it mean when a barrel is said to be a "5R"?
5R is the form of rifling I developed for use in most target barrels and in many sporting barrels.
These barrels have 5 grooves, and the lands have angular sides. I have observed that bullet jackets
will deform such that they remain closer to the R-form lands than they will to the sharp-edged
lands present in conventional-style rifling. This reduces powder fouling at the corner of the
grooves. The angled form of the lands also helps to reduce jacket failures in quick-twist barrels.