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Bureau of Alcohol, Tobacco, Firearms and Explosives

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Terminology & Nomenclature

Top Break Action

Note: The Top Break action is utilized in the design and function of rifles, shotguns and pistols. This illustration exhibits the primary characteristics of a shotgun but most component parts are applicable in a revised configuration to the rifle and pistol categories.

A diagram showing various parts of a slide/pump action weapon and their defined names: the ventilated top rib, ejector/extractor, barrel selector, etc.

Group Callout Schedule [a]



Group (1)

Various barrel configurations which may appearon this type action.
A-Single Shotgun, B-Single Rifle, C-Double Rifle, D-Combination, E-Double Shotgun

Group (2)

Two safety configurations which may appear on the available models.
A-Crossbolt, B-Top Tang

Group (3)

Two buttstock appointments available in this group.
A-Buttplate, B-Recoil Pad

  1. Group callouts identify various configurations of a specific component which may be incorporated in the function of the various models employing the bolt action in their design. However, only one type component from each callout group will appear on any given subject firearm.