The SIONICS barrels utilize 5R Rifling. 5R Rifling helps fight bullet failure due to a softer angle on the sides of the lands vs. conventional style rifling that utilizes 90° corners of the lands, which is a very hard edge. Furthermore, with 5R, you have 5 lands in the bore of the barrel. The odd number of lands does not directly oppose one another. The combination of these two things deforms the bullet less – less distortion to the bullet jacket when the bullet makes the jump from the case into the rifling. This helps fight bullet failure and increases the inherent accuracy of the barrel. Lastly, the gentler edges of lands on the 5R Rifling allow easier cleaning of the bore. The 90° corners of conventional rifling make it harder to reach lead and other contaminants when cleaning. The softer edges of the lands on 5R Rifling allow for a much more thorough cleaning process.
