NRA Metalworking & Woodworking for Gunsmithing 3 — Questions and Answers
Question 1: Which type of steel is most commonly used for rifle barrels due to its combination of strength and machinability?
- 4140 chromoly steel (Correct answer)
- 1018 mild steel
- 440C stainless steel
- Tool steel D2
Correct answer: 4140 chromoly steel
4140 chromoly steel offers an excellent balance of tensile strength, toughness, and machinability that makes it the industry standard for rifle barrels.
Question 2: When fitting a new wood stock blank to a metal action, what is the correct sequence of inletting?
- Inlet the barrel channel first, then the action
- Inlet the action first, then work outward to the barrel channel (Correct answer)
- Inlet both simultaneously using templates
- Remove wood evenly from all surfaces at once
Correct 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.
Question 3: A gunsmith is using a mill to cut a dovetail slot for a front sight. What cutter geometry is required?
- Standard end mill
- Dovetail cutter with angled sides (Correct answer)
- Ball nose end mill
- Fly cutter
Correct answer: Dovetail cutter with angled sides
A dovetail cutter has angled cutting faces that produce the characteristic trapezoidal profile needed to capture a dovetail-base sight.
Question 4: What does the Rockwell hardness scale 'C' (HRC) primarily measure in gunsmithing contexts?
- Tensile strength of the steel
- Surface hardness after heat treatment (Correct answer)
- Ductility of the metal
- Corrosion resistance rating
Correct 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.
Question 5: When checkering a pistol grip using a 60-line-per-inch pattern, what is the primary purpose of the master lines cut first?
- To create the final border of the checkering
- To establish the pattern layout and spacing guides for subsequent cuts (Correct answer)
- To remove excess wood before shaping
- To test the hardness of the stock wood
Correct answer: To establish the pattern layout and spacing guides for subsequent cuts
Master lines establish the grid spacing and direction so all subsequent cuts remain parallel and evenly spaced throughout the checkering field.
Question 6: Which heat treatment process is used to relieve internal stresses in a steel part after machining without significantly changing its hardness?
- Full annealing
- Stress relieving (Correct answer)
- Case hardening
- Normalizing
Correct answer: Stress relieving
Stress relieving heats the part below the critical transformation temperature and slow-cools it, eliminating machining stresses without major changes to hardness or microstructure.
Question 7: What finish is applied to wood stocks to raise the grain before final sanding to achieve a glass-smooth result?
- Linseed oil final coat
- A water or solvent wash to raise grain fibers before sanding (Correct answer)
- Shellac sealer coat
- Lacquer primer
Correct answer: A water or solvent wash to raise grain fibers before sanding
Wiping the sanded stock with water or a grain-raising solvent causes wood fibers to swell and stand up, which are then sanded off to produce a smoother final surface.
NRA Metalworking & Woodworking for Gunsmithing 3
Which type of steel is most commonly used for rifle barrels due to its combination of strength and machinability?