NRA Firearm Customization & Modifications 2 — Questions and Answers
Question 1: When installing a match-grade barrel on a semi-automatic pistol, which specification is most critical for reliable feeding?
- Chamber throat geometry and feed ramp angle (Correct answer)
- Overall barrel length
- External finish type
- Barrel weight
Correct answer: Chamber throat geometry and feed ramp angle
The chamber throat geometry and feed ramp angle directly control how cartridges transition from the magazine into the chamber, making them critical for reliable feeding.
Question 2: A customer wants a crisp, light trigger pull on their AR-15 for competition use. Which component replacement most directly reduces trigger pull weight?
- Buffer spring
- Trigger and hammer springs (Correct answer)
- Bolt carrier group
- Charging handle
Correct answer: Trigger and hammer springs
Replacing the trigger and hammer springs with reduced-power versions is the most direct method for decreasing trigger pull weight in an AR-15.
Question 3: What is the purpose of pillar bedding in a bolt-action rifle stock?
- To add decorative elements to the stock
- To provide rigid, dimensionally stable anchor points for action screws (Correct answer)
- To improve the stock's resistance to moisture
- To reduce the overall weight of the rifle
Correct answer: To provide rigid, dimensionally stable anchor points for action screws
Pillar bedding installs metal pillars in the stock that provide solid, consistent anchor points for action screws, preventing compression and improving accuracy.
Question 4: Which recoil pad installation technique ensures a professional, flush fit with no gaps between the pad and stock heel?
- Grinding the pad on a disc sander using a jig to match the stock angle (Correct answer)
- Cutting the pad with a utility knife freehand
- Applying epoxy to fill gaps after mounting
- Heating the pad before installation
Correct answer: Grinding the pad on a disc sander using a jig to match the stock angle
Using a disc sander with a jig to hold the stock allows precise material removal until the pad face perfectly matches the stock's angle and contour.
Question 5: When threading a rifle muzzle for a suppressor, what is the most important safety check before beginning the threading operation?
- Verifying the barrel crown condition
- Confirming the bore is centered with the barrel's outside diameter using a dial indicator (Correct answer)
- Checking the overall barrel length
- Inspecting the front sight base
Correct answer: Confirming the bore is centered with the barrel's outside diameter using a dial indicator
Confirming concentricity between the bore and the barrel's OD with a dial indicator ensures the threads are centered with the bore, preventing baffle strikes.
Question 6: A gunsmith is installing an adjustable gas block on an AR-15. What is the primary benefit this modification provides?
- Increased muzzle velocity
- Ability to tune gas flow for reliable cycling with various ammunition and suppressor use (Correct answer)
- Reduced trigger pull weight
- Improved barrel harmonics
Correct answer: Ability to tune gas flow for reliable cycling with various ammunition and suppressor use
An adjustable gas block allows the operator to fine-tune the amount of gas diverted to cycle the action, enabling reliable function with suppressors, different loads, or subsonic ammunition.
Question 7: What is the function of a trigger overtravel stop screw in a custom trigger job?
- It increases the trigger's reset distance
- It limits rearward movement of the trigger after the sear breaks, improving follow-through (Correct answer)
- It adjusts the trigger's pre-travel distance
- It sets the weight of the trigger pull
Correct answer: It limits rearward movement of the trigger after the sear breaks, improving follow-through
An overtravel stop screw limits how far the trigger travels rearward after sear break, reducing movement and helping the shooter maintain sight alignment during the shot.
NRA Firearm Customization & Modifications 2
When installing a match-grade barrel on a semi-automatic pistol, which specification is most critical for reliable feeding?