Rifling depth is .016" per side for all .45, .50 & .54 caliber barrels. .36 and .40 caliber barrels are .012" deep per side. All barrels are round bottom (radius groove) rifling. This is an old form of rifling that because of the lack of corners inthe grooves is much easier to clean and also allows the patch to seal better. All rifling is six grooves.