- Improper Assembly
- Missing Parts
- Cracks: all cracked parts are cause for concern, but especially so in the chamber-area, bolt, bolt-lugs, or buttstock.
- Bore obstructions: being either dented or bent barrels, or foreign material in barrels.
- Improper Headspace: dimensions concerning the relative space of the chamber and the bolt are not within specified tolerances.
- Improper Timing: (applies to fully automatic firearms and revolvers).
- Safety-Mechanism Malfunctions: potentially allowing a firearm with the safety mechanism supposedly engaged to unexpectedly fire.
- Worn Sear Edges: potentially allowing a firearm to unexpectedly fire when the safety mechanism is disengaged.
Firing-Pin Tips Deformed: leading to the possibility of primer-rupture.