NRA NRA Firearm Finishing & Surface Treatments 2 — Questions and Answers
Question 1: What is the purpose of 'bead blasting' or 'sandblasting' a firearm's metal parts before finishing?
- To remove metal to reduce weight
- To create a uniform matte surface texture that improves coating adhesion and hides machining marks (Correct answer)
- To harden the metal surface through peening
- To apply a chemical conversion coating in one step
Correct answer: To create a uniform matte surface texture that improves coating adhesion and hides machining marks
Abrasive blasting produces a consistent, clean surface profile that maximizes coating adhesion and gives a uniform, non-reflective appearance.
Question 2: What is 'rust bluing' and what makes it distinctive compared to hot bluing?
- A faster version of hot bluing using rust inhibitors
- A slow process that deliberately induces and converts rust to a stable black oxide finish, producing exceptional depth and durability (Correct answer)
- A cold chemical process identical to cold bluing
- A Parkerizing variant used on rusty surplus firearms
Correct answer: A slow process that deliberately induces and converts rust to a stable black oxide finish, producing exceptional depth and durability
Rust bluing repeatedly applies an oxidizing solution, allows rust to form, cards it off, and boils the part to convert the oxide — producing a deep, hard, beautiful finish.
Question 3: What does 'case hardening' refer to in the context of firearm parts and finishes?
- Hardening the cartridge case to withstand pressure
- A heat treatment process that hardens the outer surface of steel parts while leaving the core tough (Correct answer)
- A type of bluing using high heat only
- Coating the exterior of a case with chrome for appearance
Correct answer: A heat treatment process that hardens the outer surface of steel parts while leaving the core tough
Case hardening (carburizing or nitriding) diffuses carbon or nitrogen into the surface layer, making it hard and wear-resistant while the core remains ductile.
Question 4: When applying Cerakote, what temperature is typically required to cure the coating?
- Room temperature — air cures in 24 hours
- Approximately 250–300°F in a curing oven for 1–2 hours (Correct answer)
- 600°F — same as heat-bluing
- 1000°F — requires a kiln
Correct answer: Approximately 250–300°F in a curing oven for 1–2 hours
Cerakote H-series coatings are cured in an oven at approximately 250–300°F, which polymerizes the coating for maximum hardness and adhesion.
Question 5: What is 'Tennifer' (also known as Melonite or QPQ) as used on Glock slides?
- An electroless nickel coating
- A ferritic nitrocarburizing salt-bath process that diffuses nitrogen and carbon into the steel surface (Correct answer)
- A type of Parkerizing with added polymer
- A spray-on corrosion inhibitor
Correct answer: A ferritic nitrocarburizing salt-bath process that diffuses nitrogen and carbon into the steel surface
Tennifer/Melonite/QPQ is a salt-bath nitrocarburizing process that creates an extremely hard, corrosion-resistant surface layer integral to the metal, not a coating on top.
Question 6: Why is it important to maintain proper film thickness when applying spray-on coatings like Cerakote?
- Thicker coatings are always better for durability
- Improper thickness causes dimensional changes that can affect part fit, function, and tolerance-critical areas (Correct answer)
- Coating thickness has no impact on firearm function
- Only the color is affected by film thickness
Correct answer: Improper thickness causes dimensional changes that can affect part fit, function, and tolerance-critical areas
Coating thickness must stay within specification (typically 0.001" for Cerakote) to avoid binding in tight-tolerance areas like bores, chambers, and locking surfaces.
NRA NRA Firearm Finishing & Surface Treatments 2
What is the purpose of 'bead blasting' or 'sandblasting' a firearm's metal parts before finishing?