Glossary of Firearms Terms - F

F

• falling block action (also known as a sliding-block action) is a single-shot firearm action in which a solid metal breechblock slides vertically in grooves cut into the breech of the rifle and actuated by a lever. When in the top position, it is locked and resists the force of recoil while sealing the chamber. In the lower position, it leaves the chamber open to be loaded by a cartridge from the rear.

• Ferritic nitrocarburizing: A case hardening processes that diffuse nitrogen and carbon into ferrous metals at sub-critical temperatures to improve scuffing resistance, fatigue properties and corrosion resistance of metal surfaces. Also called nitriding.

• fire forming: the process of reshaping a metallic cartridge case to fit a new chamber by firing it within that chamber.

• forcing cone: The tapered section at the rear of the barrel of a revolver that eases the entry of the bullet into the bore.

• fouling shot: A fouling shot is a shot fired through a clean bore, intended to leave some residue of firing and prepare the bore for more consistent performance in subsequent shots. The first shot through a clean bore will behave differently than subsequent shots through a bore with traces of powder residue, resulting in a different point of impact. Also, the Fouling Shot Journal, a publication of the Cast Bullet Association

• forward assist: A button, found commonly on M16 and AR-15 styled rifles, usually located near the bolt closure, that when hit will push the bolt carrier forward, ensuring that the bolt is locked.

• fouling: The accumulation of unwanted material on solid surfaces. The fouling material can consist of either powder, lubrication residue, or bullet material such as lead or copper.

• frangible: A bullet that is designed to disintegrate into tiny particles upon impact to minimize their penetration for reasons of range safety, to limit environmental impact, or to limit the danger behind the intended target. Examples are the Glaser Safety Slug and the breaching round.

• frizzen: an "L" shaped piece of steel hinged at the rear used in flintlock firearms. The flint scraping the steel causes a shower of sparks to be thrown into the flash pan.