- 01: Introduction
- 02: History
- 03: Propellants, Firearms, and Ammunition Development
- 04: Modern Firearms Manufacture
- 05: Small Arms Ammunition
- 06: Evidence Handling Procedures
- 07: Equipment and Instrumentation
- 08: Examination of Firearms
- 09: Cartridge and Shotshell Examination
- 10: Characterization and Evaluation of Fired Projectiles
- 11: Bullet Comparison and Identification
- 12: Gunshot Residue and Distance Determination
- 13: Toolmark Identification
- 14: Communicating Results
- Resources
U.S. Department of Justice, Office of Justice ProgramsNational Institute of JusticeThe Research, Development, and Evaluation Agency of the U.S. Department of Justice
Lapping
Home > Modern Firearms Manufacture > Rifled Barrels > Lapping
Any cutting operation, including reaming, leaves microscopic projections or burrs on the processed surface. After reaming, an in-process barrel can be taken to the rifling stage and still produce a decent barrel. However, high-grade barrels or those destined to fire soft lead bullets may be polished (called lapping) prior to rifling. Typical bore lapping uses an abrasive paste on a soft lead cylinder. It is passed through the bore several times, reducing any burrs. The size of imperfections is minimized by applying a fine grinding paste. Finer grade grit paste produces smoother surfaces. If required, pastes (properly graded for grit size) can produce a mirror finish in metals.
