BudsGunShop.com - Is this shotgun a Benelli M4 clone?

Yes, it is a benelli 1014 clone.
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The S4 shotgun is compatible with M-1014 Parts and Accesories for further customization.
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sdsimports.com/sdsimports-s4-shotgun-p/s4.htm

Carl, it is a Benelli 1014 Clone and uses 1014 parts and accessories. The SDS Imports S-4 takes the basic semi-automatic shotgun and increases its capabilities by adding a Picatinny rail, adjustable sights, and a pistol grip stock. The receiver mounted rail is perfect for a red dot optic. The pistol grip stock enhances control and retention. In addition to the rail and pistol grip, the S-4 features a 18.5" barrel with a 3" chamber, adjustable rear sight, and an elevated fiber optic front sight, and a rubber recoil pad. Included are (3) Chokes: Improved Cylinder, Modified, Full Chokes.