The standard GP100 has barrels from 2.5 inches up to 6 inches. Calibers include 22LR, 327 magnum, 357 magnum, 10mm and 44 special. Most of the offers are 357 magnum. You can get the 357 version with 2.5 inch, 3 inch, 4.2inch and 6 inch barrels. Most of the other calibers only ...