NRA Firearm Mechanisms & Action Types Flashcards

What is the function of the extractor in a semi-automatic firearm?

Answer: It grips the case rim and pulls the spent case from the chamber

The extractor hooks the case rim and withdraws the spent cartridge from the chamber as the bolt moves rearward.

What does 'locking lugs' refer to in bolt-action and semi-automatic rifle design?

Answer: Protrusions on the bolt that rotate into recesses to lock the action closed during firing

Locking lugs are projections on the bolt that engage recesses in the receiver or barrel extension to contain chamber pressure during firing.

Which action type is most commonly found on double-barrel shotguns?

Answer: Break-action

Break-action shotguns hinge at the receiver, allowing the barrels to tilt downward for loading and unloading.

What is the purpose of the ejector in a firearm?

Answer: It strikes the spent case to propel it clear of the action

The ejector contacts the case head as the bolt moves rearward, striking it to flip the case out of the ejection port.

What is 'feeding reliability' primarily dependent on in a semi-automatic pistol?

Answer: The geometry of the feed ramp and magazine lip angle

Feed reliability depends on the feed ramp angle guiding rounds smoothly into the chamber and properly tuned magazine lips controlling cartridge presentation.

What is the purpose of a gas regulator on some gas-operated rifles?

Answer: It allows adjustment of the amount of gas used to cycle the action

A gas regulator lets the shooter increase or decrease gas flow to ensure reliable cycling with different ammunition or when using a suppressor.