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Inertia Driven® System

Stoeger’s semi-auto shotguns feature the proven Inertia Driven® system. It’s the simplest, fastest, cleanest, strongest, most reliable operating system in the world.

This is the system that earned inertia-operated shotguns their reputation for being among the fastest cycling, most reliable shotguns in the world.
Its action…

  • Features a patented inertia bolt assembly with a rotating locking head
  • Ensures a positive steel-to-steel lock-up
  • Provides the Stoeger M3000 and M3500 semi-autos ultimate strength and reliability

Here’s How It Works


Step 1 Chambering

As the bolt assembly moves into battery, the locking head pin moves along a curved track in the bolt body. It rotates the steel bolt head into engagement with the steel barrel extension. The cartridge drop lever is down.

Step 2 Firing

When the trigger is pulled, every part of the shotgun except the bolt body moves rearward. The curved track in the bolt body is moving forward relative to the rest of the gun. The curved track presses against the locking head pin. This turns the bolt head even more tightly into the barrel extension. At the same time, the inertia spring is compressed between bolt head and body. The cartridge drop lever moves up, allowing a shell to move from the magazine to the carrier.

Step 3 Recoil

Near the end of the recoil cycle, chamber pressure drops to a safe level. The gun’s rearward motion slows. The heavy inertia spring then thrusts the bolt assembly rearward. That action unlocks the rotating bolt head, extracting the spent shell from the chamber and pulling it against the ejector.

Step 4 Ejection

As the empty shell exits the receiver, the energy of the moving bolt assembly re-cocks the hammer and compresses the recoil spring on the magazine tube. The recoil spring then thrusts the bolt assembly forward. This action lifts the oncoming shell into position and chambers a fresh cartridge. Within a fraction of a second, the gun is ready to fire again.

It’s Different from Gas-Operated Systems

The proven inertia bolt assembly is different from traditional gas-operated systems. The Inertia Driven® system keeps a gun’s action cleaner. That’s because gas and burnt powder are expelled through the barrel and are not used to cycle the action.

The system has…

  • Fewer moving parts
  • No gas cylinders
  • No O-rings or other complicated parts

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