The Benelli Bellmonte Brown II MK2 is semiautomatic shotguns operated by an inertial system , featuring a geometric locking phase driven by an oscillating block. The inertial system delivers the power of a locked breech shotgun, concentrating 100 percent of the gases behind the shot wad for extra power and range . The models can handle any loads from 2 34 " ( 70 mm ) up to the heaviest 3 " ( 76 mm ) magnums.