NRA Firearm Repair & Restoration Techniques 2 — Questions and Answers
Question 1: When re-crowning a rifle barrel, which tool is most appropriate for producing a target-grade recessed crown?
- Flat-face end mill
- 11-degree carbide cutter with a pilot (Correct answer)
- Standard drill bit run in reverse
- Bench grinder with a wire wheel
Correct answer: 11-degree carbide cutter with a pilot
An 11-degree carbide cutter with a pilot centers itself in the bore and cuts a consistent, precise recessed crown that protects the rifling and improves accuracy.
Question 2: A revolver exhibits cylinder timing issues where the cylinder does not lock up fully before the hammer falls. Which component is the MOST likely cause?
- Rebound slide spring
- Cylinder hand (pawl) (Correct answer)
- Mainspring strut
- Firing pin return spring
Correct answer: Cylinder hand (pawl)
The cylinder hand (pawl) advances and indexes the cylinder; wear on its tip or engagement surface causes the cylinder to under-rotate and fail to lock up in time.
Question 3: What is the correct procedure when using a barrel vise and action wrench to remove a stubborn barrel from a rifle action?
- Apply heat to the receiver threads with a torch, then turn with the action wrench
- Clamp the barrel firmly in the vise and rotate the action wrench counter-clockwise when viewed from the muzzle (Correct answer)
- Clamp the barrel firmly in the vise and rotate the action wrench clockwise when viewed from the muzzle
- Remove the barrel extension first, then use an impact driver on the shank
Correct answer: Clamp the barrel firmly in the vise and rotate the action wrench counter-clockwise when viewed from the muzzle
Standard barrel threads are right-hand, so the action (receiver) must be turned counter-clockwise (when viewed from the muzzle) to unscrew it from the barrel.
Question 4: During stock refinishing, a gunsmith discovers checking that has been partially filled with old finish. The best method to restore crisp, sharp checking is to:
- Apply acetone with a stiff brush and then re-checker over the filled grooves
- Use a single-cut checkering file to deepen and clean out the grooves, then re-run border lines (Correct answer)
- Sand the stock flat and apply new checkering at a coarser LPI
- Strip the stock with caustic stripper and allow the checking to self-clear
Correct answer: Use a single-cut checkering file to deepen and clean out the grooves, then re-run border lines
A single-cut checkering file is run through each groove to remove old finish and re-define the diamonds before re-cutting the borders.
Question 5: A semi-automatic pistol consistently fails to feed the last round from a magazine. The most logical first diagnostic step is to:
- Replace the recoil spring assembly
- Inspect and measure the magazine follower angle and spring tension (Correct answer)
- Polish the feed ramp to a mirror finish
- Replace the extractor with an oversized unit
Correct answer: Inspect and measure the magazine follower angle and spring tension
Last-round feed failures most often result from a weak or canted magazine follower that does not present the final cartridge at the correct angle for the slide to chamber it.
Question 6: Which rust bluing step is responsible for converting the initial red iron oxide into the desired black magnetite (Fe3O4)?
- Boiling the part in distilled water (Correct answer)
- Carding the part with a wire wheel or card brush
- Applying the rusting solution with a swab
- Dipping the part in a degreasing solution
Correct answer: Boiling the part in distilled water
Boiling the rust-coated part in distilled water converts the red ferric oxide (Fe2O3) to black magnetite (Fe3O4), which is the durable rust-blue finish.
Question 7: A bolt-action rifle has excessive headspace confirmed by gauge. Which repair approach is most appropriate before condemning the barrel?
- Set the barrel back one thread and re-cut the chamber (Correct answer)
- Install a Sako-style extractor to compensate for the extra headspace
- Stake the barrel-to-receiver junction with a center punch
- Lap the bolt face to advance the locking lugs forward
Correct answer: Set the barrel back one thread and re-cut the chamber
Setting the barrel back one thread shortens the chamber enough to reduce headspace to within specification, which is far more practical than replacing the barrel.
NRA Firearm Repair & Restoration Techniques 2
When re-crowning a rifle barrel, which tool is most appropriate for producing a target-grade recessed crown?