Inertiasulku

Inertiasulku is a Finnish term that translates to "inertia lock" or "inertia bolt." It refers to a mechanical component, often found in older firearms and some specialized machinery, designed to prevent accidental discharge or unintended operation. The core principle behind an inertiasulku is its reliance on the inertia of the moving parts to ensure proper function.

In a firearm context, an inertiasulku mechanism typically involves a bolt or locking piece that is held in a secure position by the inertia of its own mass or the force of a spring during normal operation. Only when subjected to the specific forces generated by firing or cycling the mechanism does the inertia allow the bolt to move or disengage. This design can contribute to a simpler and more robust action compared to more complex safety mechanisms.

The term is most commonly associated with certain types of semi-automatic shotguns, particularly those designed in the mid-20th century. These firearms utilize the recoil and the inertia of the bolt carrier to cycle the action. The inertiasulku ensures that the bolt remains locked until sufficient energy is available from the firing impulse to overcome the inertia and unlock the action for ejection and reloading. While less common in modern firearms due to the prevalence of gas-operated or simpler recoil-operated systems, the concept of inertia as a functional element in mechanical design remains relevant.