Had the drive some time ago, to rifle one of the tubes of a .410 SXS (probably the left full choked tube). Never bought one to try it out & Brad didn't want to be do this to his.

Using an 18" or 20" twist .45 barrel as a guide, would be a fairly easy endeavour.

The 3" (or 2 1/2" for that matter) case would hold all the BP you would want to shoot with a 220gr. bullet.