Inertia-driven shotguns are light, clean-running, and beautifully simple—but that simplicity comes with a unique reliability challenge. Unlike gas- or recoil-operated shotguns, an inertia gun depends on the movement of the entire firearm to cycle. That gives it a narrower Window of Reliability, where ammunition, shooter technique, friction, and even lubrication can determine whether the action runs—or short-strokes. And here’s where things get interesting: lubricating an inertia shotgun like any other semi-auto isn’t necessarily the best approach. Our testing found that inertia guns operate in an energy range closer to rimfires than many other semi-auto shotguns. That changes not only what lubricant works best, but where you should—and shouldn’t—put it.