Our barrels are 6 groove, cut rifled, 1:10 Twist Right Hand, fully QC inspected, double honed (rough and finish) to produce the smoothest bore possible, with a Max Roughness Average (RA) of 12. Finished bore dimensions are held to +/- 0.0005" tolerance from nominal groove and bore dimensions but the dimensions are uniform to within 0.0002 for maximum consistency, accuracy and quality.