This shotgun is tough and versatile. Out of the box the MC312 runs 12 gauge 3-1/2 inches. We even tested target loads, 12 gauge hot 3-1/2 inches, mixed in the same mag tube and the shotgun still functioned. This is a very difficult task for most shotguns as it requires the bolt to cycle back far enough to load the 12 gauge 3-1/2 inches, but using only the energy from a target load 12 gauge 2-3/4 inches. We really abused this gun in testing. We ran 700 rounds continuous leaving no time to cool, we mixed and matched ammo in a single mag tube, and we put it through some of the most grueling tests we could come up with. We ran the first 5000 rounds with zero cleaning, then ran a 10,000 round endurance test without replacing any parts. For the last test, we disassembled 5 shotguns, placed the parts in a box, mixed the parts up and reassembled the guns with a random selection. The MC312 fired with no adjustment needed. Features: Polymer stock and forend Shell release Rubber butt pad Sling swivel nipple Rotating bolt