Retay Arms Inertia Plus Shotgun Action Explained

    Earlier we have reported that Retay Arms Masai Mara shotgun will become available for the US market. Among a number of advertised features, there is one which is especially interesting. It is their Inertia Plus system. The name of the system itself hints that there is something more than an ordinary inertia system. Let’s see what it is about.

    Images by Retay Arms

    First things first, just in case you don’t know about the inertia operation, let me briefly describe it. Basically, inertia operated firearms use the energy generated from the recoiling firearm which gets accumulated into a spring then used to cycle the action. Such firearms have a floating part (mostly the bolt carrier). When the shot is fired and the gun starts to recoil back, the floating part obeys the inertia law and shows a tendency to stay in rest. As a result, a spring sandwiched between the moving gun and the floated part gets compressed and cycles the action when extending.

    What makes the Retay Arms Inertia Plus system different from the above described basic principle is the special torsion bar built into the bolt body. That torsion bar rides on the locking/unlocking cam slot of the bolt carrier and winds an internal spring during the unlocking phase. Once the action is cycled and the bolt head starts to rotate to lock the action that pre-winded spring applies additional rotational force to ensure a more reliable lockup.

    Here is an excerpt from the Retay Arms press released followed by a video showing an animation of the described action:

    The Retay Arms Inertia Plus ™ system uses a specially adapted torsion mechanism built into the body of the system’s bolt head. The mechanism is charged with the kinetic energy produced as the floating bolt-head rotates backward out of battery during the initial phase of recoil cycle.

    This kinetic energy is stored momentarily within the bolt body as the bolt body moves backward in the second phase of recoil cycle. During the bolt body’s recovery phase the torsion mechanism releases the stored kinetic energy to apply additional forward rotational force that assists the forward movement of the bolt-head ensuring that it locks securely into battery with the barrel chamber, making the action ready for the next shot under all conditions.    

    The inertia plus system is supposed to increase the reliability of the shotgun in different climate conditions and with different loads. Considering that they are developing this system from 2015, I think the chances are good that they have perfected it to work as advertised.

    Hrachya H

    Managing Editor

    Being a lifelong firearms enthusiast, Hrachya always enjoys studying the history and design of guns and ammunition. He also writes for and
    Should you need to contact him, feel free to shoot him a message at [email protected]