The Hatfield SAS 12 gauge uses an innovative operating system that blends gas and inertia operations to produce a fast cycling moderate recoil semi-auto shotgun. The gas piston moves only one inch to kick the bolt rearward and start the operating cycle. Fewer moving parts mean increased reliability in the field. The gas/inertia system works dependably with most commercial 2.75" and 3" magnum shells.

Hi Randy, it has both actually Gas and Inertia SPECS-- Hatfield SAS USA12T - Semi Automatic Shotgun - Gas/Inertia Operated - 12 Gauge - 5 Rounds - 20" Barrel - Fixed Cylinder Bore - Blade Front Sight - 3" Chamber - High Strength Aluminum Receiver - Full Length Rail - Adjustable Synthetic Stock - Black Finish - Overall Length 40" - Weight: 7.2 lbs.

This shotgun uses both Gas and Inertia operation Randy ----(Specifications and Features): - Hatfield SAS USA12T - Semi Automatic Shotgun - Gas/Inertia Operated - 12 Gauge - 5 Rounds - 20" Barrel - Fixed Cylinder Bore - Blade Front Sight - 3" Chamber - High Strength Aluminum Receiver - Full Length Rail - Adjustable Synthetic Stock - Black Finish - Overall Length 40" - Weight: 7.2 lbs.

It is a gas/inertia system . The gas piston moves only one inch to kick the bolt rearward and start the operating cycle. Fewer moving parts mean increased reliability in the field. The gas/inertia system works dependably with most commercial 2.75" and 3" magnum shells.Specifications and Features:
Hatfield SAS USA12T
Semi Automatic Shotgun
Gas/Inertia Operated
12 Gauge
5 Rounds
20" Barrel
Fixed Cylinder Bore
Blade Front Sight
3" Chamber
High Strength Aluminum Receiver
Full Length Rail
Adjustable Synthetic Stock
Black Finish
Overall Length 40"
Weight: 7.2 lbs