Detailed Barrel Specifications: Material used is 416R Stainless Steel heat treated to 40 Rockwell C. All barrels are broached and manufactured from bar stock material or forgings, depending on availability. All are guaranteed for accuracy. All barrels are 1 in 16 twists and 6 lands and grooves irrespective of caliber. This is a twist rate that will allow the barrels to shoot a wide variety of bullets with excellent accuracy.  Bores are as follows: 9mm/38 Super . . . . . . . . . . . . 355 to .3555 Groove & .348 Bore. 40 S&W/10mm . . . . . . . . . . . . 400 Groove & .390 Bore 45 ACP . . . . . . . . . . . . . . . . . . . 451 Groove & .442 Bore  Hood and bottom lug is oversized and requires fitting. Chambers are cut short and will require correct head spacing after fitting. Fitting instructions are supplied.  Detailed Barrel Bushing Specifications: All bushing are made out of 17-4 Stainless Steel for maximum tensile strength. Solid bushings and Oversize Spherical Housings have outer diameters at or more than .703 inches. The distance from the flange to the locking cam is reduced to allow accurate fitting so as to prevent in line movement. Drop in Spherical Housings are at .698 inch outer diameter which is the largest OD available so as to fit in all types 1911 auto pistols. Spherical Rings are manufactured from either STRESSPROOF� or FATIGUE-PROOF� carbon steel which are later coated with TiN (Titanium Nitride) which provides surface hardness and lubricity. Rings are selected to be .001 inches over the OD of the barrel. Ring removal and insertion instructions are provided. Bushing wrenches are sold separately.