Mixed Deck — All NRA Topics Flashcards

What is the primary reason a gunsmith would use a chamber reamer stop collar when chambering a barrel?

Answer: To control how deep the reamer cuts, preventing over-chambering and tight headspace

A stop collar limits the reamer's cutting depth, allowing the gunsmith to creep up on the correct headspace incrementally without accidentally cutting the chamber too deep.

What determines the lock time of a firearm?

Answer: The time from trigger release to primer ignition

Lock time is the elapsed time between trigger release and primer ignition, influenced by firing pin weight and spring tension.

What is 'sight radius' on a firearm?

Answer: The distance between the front and rear sights

Sight radius is the measured distance between the front and rear sights; a longer radius reduces angular aiming error and generally improves practical accuracy.

Which wood grain orientation provides the greatest impact resistance for a rifle stock?

Answer: Straight vertical grain running the length of the stock

Straight vertical grain (quarter-sawn) running lengthwise is strongest because wood fibers align with the primary stress direction during recoil.

What does the Rockwell hardness scale 'C' (HRC) primarily measure in gunsmithing contexts?

Answer: Surface hardness after heat treatment

The Rockwell C scale uses a diamond cone indenter under load to measure surface hardness, commonly used to verify heat treatment results on hardened firearm parts.

When fitting a new wood stock blank to a metal action, what is the correct sequence of inletting?

Answer: Inlet the action first, then work outward to the barrel channel

Starting with the action inletting establishes the critical fit at the receiver, then extending the barrel channel ensures proper alignment throughout.

What is the term for the pressure spike that occurs when the bullet first begins to move from the case?

Answer: Chamber pressure

Chamber pressure is the pressure generated inside the cartridge case when the propellant ignites, typically measured in PSI or CUP at its peak just as the bullet begins moving.

Why should a gunsmith test the fit of all parts AFTER applying a new finish?

Answer: Coatings add measurable thickness that can affect tolerances, requiring fitting to restore proper clearances

Even thin coatings like Cerakote add material thickness that can cause binding in tight-tolerance areas, requiring the gunsmith to fit parts back to specification.

What is the function of the gas port in a gas-operated semi-automatic rifle?

Answer: To bleed propellant gas to cycle the action

The gas port allows a portion of propellant gas to bleed off from the barrel and redirect it to operate the bolt carrier group.

Which type of sighting system requires the most precise and permanent installation due to its zero-sum adjustment method?

Answer: Fixed iron sight (dovetail style)

Fixed dovetail sights have no elevation or windage adjustment screws — they must be precisely drifted or cut to the correct position during installation to achieve proper zero.

What does it mean if a firearm exhibits 'trigger creep'?

Answer: The trigger moves rearward a significant distance before the sear releases, instead of a clean break

Trigger creep is the takeup or movement of the trigger prior to the sear release, often felt as a gritty or mushy movement before the shot breaks.

What is the purpose of a 'Dremel tool' or die grinder in gunsmithing, and what caution applies?

Answer: Used for light deburring, polishing, and fitting work — caution: removing too much metal can render parts unsafe or non-functional

Rotary tools are useful for light fitting and polishing but must be used carefully, as excessive material removal can weaken or destroy critical components.

What is parallax error in a rifle scope, and when does it occur?

Answer: The apparent movement of the reticle relative to the target when the shooter's eye moves off the optical axis

Parallax error occurs when the target image and reticle are focused on different planes inside the scope, causing the reticle to appear to shift relative to the target as the shooter's eye position changes.

Which lathe operation is used to cut the crown at the muzzle end of a rifle barrel to protect rifling and ensure accuracy?

Answer: Recessing or countersinking using a tool ground to the desired crown angle

A crown is cut by recessing the muzzle face at a specific angle or radius using a properly ground cutting tool to uniformly protect all rifling lands at the exit point.

What lubricant is appropriate for a firearm's wooden stock hardware?

Answer: Linseed oil or stock finish appropriate to the wood type

Linseed oil or appropriate stock finishing oils condition and protect wooden stocks without the mineral oil components that can swell or discolor wood.

What is case annealing used for in ammunition reloading?

Answer: To soften the case neck and shoulder to restore ductility after repeated firing

Annealing uses controlled heat to soften brass case necks and shoulders that have become work-hardened from repeated firing and resizing, extending case life.

When installing a set trigger (double-set trigger) system on a custom rifle, what critical adjustment must be verified for safe operation?

Answer: That the set trigger cannot release the sear when jarred or dropped without deliberate actuation

A set trigger must be tested for drop safety to ensure that an accidental jar or impact cannot cause an unintended discharge when the trigger is in the set position.

What is the sear's role in a firearm's trigger group?

Answer: It holds the hammer or striker in the cocked position until released by the trigger

The sear engages a notch on the hammer or striker to hold it cocked and releases it when the trigger is pulled.

What is the purpose of the striker in a striker-fired pistol?

Answer: It serves as both the hammer and firing pin combined into one component

In striker-fired pistols, the striker acts as a combined hammer and firing pin, driven by spring tension to strike the primer.

What does checking for 'cylinder lockup' in a revolver assess?

Answer: Whether the cylinder indexes correctly and locks solidly in alignment with the barrel under firing conditions

Cylinder lockup checks that the cylinder rotates to full index and is firmly locked in alignment with the barrel and forcing cone, preventing off-axis bullet travel.