The Weatherby 18i Synthetic 12 Gauge Semi-Auto Shotgun, 3.5-Inch Chamber (Weatherby part no. ISY1228SMG) is a 12 gauge inertia-driven semi-auto with a 3.5-inch Supermag chamber. Weatherby builds the 18i on a field-proven inertia recoil system that cycles reliably and keeps the gun evenly weighted. The advanced polymer stock is shim adjustable and carries an elastomer insert to cut felt recoil, and a matte finish covers the metalwork. A full ventilated rib and a high-luminosity LPA fiber front sight make target acquisition quick even in poor light. It is a shotgun for waterfowlers and turkey hunters who need to run the largest magnum loads.

Key Specifications

• The gauge is 12, the standard choice for waterfowl and big-bird loads.
• The chamber is 3.5 inches, which handles the largest magnum shells on the market.
• The stock and forearm are synthetic polymer with an elastomer insert, which cuts felt recoil and sheds weather.
• The stock is shim adjustable with a soft-touch cheek rest and aggressive texture in the palm and foregrip.
• The metalwork has a matte finish that keeps glare down in the field.
• The sight is an LPA fiber front sight on a full-length ventilated rib, which is easy to pick up in poor light.
• The choke system is CRIO Plus with five tubes, from cylinder to full, for matching the pattern to the game.

Frequently Asked Questions

What chamber length does this 18i Synthetic have? This version has a 3.5-inch chamber, which Weatherby describes as a Supermag chamber for the largest magnum loads.

Is the stock adjustable? Yes. The advanced polymer stock is shim adjustable so the fit can be tuned to the shooter.

What chokes does it use? It is set up for the CRIO Plus choke system and comes standard with five choke tubes.

Buy the Weatherby 18i Synthetic 12 Gauge Semi-Auto Shotgun, 3.5-Inch Chamber

The 18i Synthetic gives magnum-load shooters a weather-ready inertia gun. Order it from our Lubbock, Texas gun shop for fast, insured shipping to your FFL, and browse more semi-auto shotguns while you are here.