Mesa Tactical SureShell Polymer 6-Shot Sidesaddle (Mossberg 500/590)

The Mesa Tactical SureShell polymer sidesaddle is the standard receiver-mounted shell carrier for the Mossberg 500, 590, 590A1, and Maverick 88. It puts six 12-gauge shells on the left side of the receiver where they can be stripped for an emergency reload without breaking the firing grip or fishing through a pocket. With the factory 5+1 or 8+1 magazine tube and a six-round sidesaddle, total on-gun capacity for the 590A1 reaches 14 rounds without belt or pouch storage.

Installation uses the factory trigger pin holes: pop out the trigger pins, slide the sidesaddle plate over the receiver, and reinstall the longer pins included in the kit. No drilling or permanent modification is required, and the carrier is fully reversible. Polymer construction keeps weight under 6 ounces, which matters because anything bolted to a pump shotgun moves with every cycling stroke. The elastic shell loops grip 12-gauge hulls firmly enough to survive recoil, but not so tightly that you can't pull a shell one-handed under stress.

Mesa Tactical also makes an aluminum SureShell with an integrated Picatinny rail (around $110) for shooters who need optic mounting on top of the receiver. For most defensive 500/590 builds, the polymer version is the right call: the Mossberg's factory tang safety and existing top rail (590A1) handle optic and accessory mounting on their own, and the weight savings is meaningful on a pump gun.