- 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
Chambering and Throating
Home > Modern Firearms Manufacture > Rifled Barrels > Chambering and Throating
Chamber reamer
All cartridge firearms, except revolvers, require the enlargement of the rear portion of the bore to accept a cartridge. The enlarged section is the chamber. For a cartridge with relatively straight sidewalls close to bore diameter (e.g., 30 US Carbine), a chamber reamer can produce the finished chamber in one operation. However, for bottleneck cartridges (e.g., 30-06 Springfield), the main body of the chamber can be twice the bore diameter. Removing this extra material rapidly with low-cost tooling saves wear to expensive chamber reamers. Less expensive roughing reamers can be used or the chamber can be roughed out by other methods. Step drilling with standard twist drills or the formation of a partial chamber in a hammer-forged barrel accomplishes the goal of preserving critical finishing reamers.
The intersection of the chamber with the rifling must be carefully tapered to reduce the engraving forces on a fired bullet. This area of the barrel is the throat. For mass-produced commercial and military firearms, the throating reamer is commonly an integral part of the chambering reamer. For special throating needs, separate throating reamers may be used. Nonstandard throating is usually the realm of the custom gunsmith. Throat dimensions for standard cartridges are specified in industry barrel/chamber drawings.
