5R Rifling

5R rifling differs from conventional rifling in two ways. First, it uses five lands instead of the usual four or six, arranged so that no land sits directly across the bore from another land; each one faces a groove instead. Second, the walls of the lands and grooves are sloped rather than cut at a sharp right angle, so the transition from groove floor to land top is a ramp.

That geometry engraves the bullet more gently, deforming the jacket less as it takes the rifling and leaving the projectile better balanced. The sloped walls also give residue fewer sharp corners to lodge in, which many shooters credit with reduced fouling and easier cleaning. 5R is available in a range of twist rates, and choosing the right twist rate for the bullet still matters as much as the land profile.