NRA Firearm Mechanisms & Action Types Flashcards

What is the primary role of the recoil spring in a semi-automatic pistol?

Answer: It returns the slide to battery and absorbs recoil energy

The recoil spring stores energy as the slide moves rearward and returns the slide forward to chamber the next round.

In a double-action/single-action (DA/SA) pistol, what happens on the first trigger pull?

Answer: The trigger both cocks and releases the hammer

On the first DA pull, the trigger performs two actions — cocking the hammer and releasing it — resulting in a longer, heavier pull.

What is headspace in a firearm?

Answer: The distance from the bolt face to the datum line in the chamber

Headspace is the critical measurement from the bolt face to the point where the cartridge is stopped in the chamber.

Which part of a revolver rotates to align each chamber with the barrel?

Answer: The cylinder

The cylinder rotates with each trigger pull or hammer cock to index a new chamber in line with the barrel.

What is the purpose of a firing pin block (drop safety)?

Answer: It prevents the firing pin from moving unless the trigger is deliberately pulled

A firing pin block prevents accidental discharge if the firearm is dropped by blocking the firing pin unless the trigger is fully depressed.

In a gas-operated semi-automatic rifle, where is propellant gas typically tapped to cycle the action?

Answer: From a port in the barrel forward of the chamber

Gas is tapped from a port drilled in the barrel, typically several inches forward of the chamber, to drive the bolt carrier rearward.