5R Rifled Barrel
5R is the form of rifling developed by Boots Obermeyer for use in most target barrels and in many sporting barrels. These barrels have 5 grooves, and the lands have angular sides. It has been 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.