Chamber Reamer
The precision cutting tool a gunsmith runs into a barrel blank to machine the chamber to SAAMI or custom dimensions for a given cartridge.
A chamber reamer is the multi-fluted cutting tool that machines the chamber into the breech end of a barrel. Ground to the exact profile of a cartridge, it cuts the body, shoulder, neck, and throat in one operation so the finished chamber matches a published specification or a custom print the smith has chosen.
Reamers come in standard SAAMI configurations as well as tighter match versions with controlled neck diameters and freebore for handloaders. The gunsmith advances the reamer slowly with cutting oil and checks progress against gauges to land the correct headspace. Because reamer geometry defines the chamber the cartridge lives in, selecting and running it is a core piece of barrel gunsmithing.