Customized Mossberg 500 12 Gauge Pump-Action with ATI Adjustable Stock, Red Dot, Rails, and 18.5 in Ported Cylinder-Bore Barrel
This Mossberg 500 12-gauge stands out as a purpose-built, customized pump shotgun with a compact 18.5-inch ported, cylinder-bore barrel and a suite of functional upgrades. It is chambered for both 2-3/4 in and 3 in shells, retains the standard 5+1 capacity, and features a receiver-top Picatinny rail with a compact reflex-style red dot installed. The ATI 6-position adjustable AR-style stock with rubber recoil pad offers an approximately 11–15 inch length-of-pull range, enhancing fit and control.
Condition
Overall Condition: Good condition, showing some signs of prior use and handling.
Bore Condition: Good - Clean, well-maintained, minor wear marks.
Bore Rifling: Not applicable — smoothbore cylinder-bore barrel.
Specific Condition Notes: Scuffs to the finish are present throughout. There is a scratch on the left side of the receiver, and normal wear is visible on the magazine tube.
What’s Included
- Optic: Compact reflex-style red dot optic (installed on receiver-top Picatinny rail)
- Rail: Receiver-top Picatinny rail (installed)
- Stock: ATI 6-position adjustable buttstock (installed)
- Shell Carrier: Buttstock-mounted shell carrier (installed)
- Rail: Clamp-on barrel/magazine-tube accessory rail assembly (installed)
- Shell Carrier: Clamp-on 5-shell carrier at barrel/mag-tube area (installed)
- Fore-end Accessory: Mossberg-branded nylon forend strap (installed)
The heart of this build is a Mossberg 500 12-gauge with an 18.5-inch barrel that is marked “18 1/2 IN. — CYLINDER BORE” and ported near the muzzle. It is chambered for 2-3/4 in and 3 in shells and maintains the standard 5+1 magazine configuration. The matte black metalwork and aluminum alloy receiver keep weight manageable while maintaining durability.
Furniture and fit are enhanced by an ATI 6-position adjustable AR-style buttstock with a rubber recoil pad, delivering an approximate 11–15 inch length-of-pull range. A separate synthetic pistol grip and a rear sling stud round out the user-focused stock setup, while the ribbed synthetic fore-end includes a Mossberg-branded nylon strap for added control.
Optics and accessories are well-supported. A receiver-top Picatinny rail is installed and hosts a compact reflex-style red dot optic. Forward of the receiver, a clamp-on barrel/mag-tube accessory rail assembly expands mounting options. Ammunition management is streamlined by two carriers: a clamp-on 5-shell carrier at the barrel/mag-tube area and a buttstock-mounted shell carrier.
Operation retains the proven Mossberg 500 features, including an ambidextrous top-tang safety, twin action bars, and dual extractors. Markings include “Mossberg — Made in U.S.A., North Haven, Conn.” with warning text referencing Eagle Pass, TX, underscoring its American manufacture and the lineage of the 500 series.