The rifle chamber is located within the barrel, which is threaded into the rifle receiver. Re-chambering requires you to select a cartridge larger than the one with which you begin so that you can remove metal, enlarging the chamber to fit the new cartridge. Do not change calibers as this will require re-boring the barrel. Usually, re-chambering requires replacing the ejector on the bolt.
Remove the rifle barrel from the receiver using a rifle barrel wrench. This will require extreme torque and the rifle receiver must be held securely within a gun vice.
Center the rifle chamber, exactly dead center, with the drill. The tolerance during this procedure is 1/10,000 of an inch or better.
Carefully measure the amount of depth needed for the new chamber and lock the drill stop so that the bit does not exceed the maximum chamber depth for the new cartridge. The tolerance during this procedure is 1/10,000 of an inch or better.
Slowly drill out the new chamber, using drilling coolant/lubricant to keep the metal temperature as low as possible. High metal temperatures will reduce the strength of the chamber walls and may produce a chamber that is unable to withstand the high pressures produced by a rifle cartridge.
Re-attach the rifle chamber/barrel to the receiver, using the head-space gauge placed into the chamber, to ensure that proper head spacing is maintained with the new cartridge. Tighten the barrel until the head-spacing gauge allows the bolt to close properly. The head-spacing gauge will ensure that the bullet is supported by the bolt so that excessive expansion of the brass cartridge does not occur and separate the base of the brass cartridge from its body.
Items you will need
- Gun vice
- Rifle barrel wrench
- Head-space gauge for the new cartridge
- Drill bit matching the new chamber specifications
- Calipers (accurate to within 1/10,000 of an inch)
- Drilling coolant/lubricant
- New ejector pin (to match the new cartridge)
- Use light loads when testing the new chamber and gradually work you way up to full powder charges.
- Re-chambering a rifle is a demanding project, requiring you to stay within very tight tolerances. Professional gunsmithing experience is recommended.
- "Gunsmithing: The Complete Sourcebook for Firearms Design, Construction, Alteration, and Restoration for amateur and Professional Gunsmiths"; Roy F. Dunlap; 1963
- "Gunsmithing -- Rifles"; Patrick Sweeney; 1999
- "Professional Gunsmithing: A Textbook on the Repair and Alteration of Firearms"; Walter J. Howe; 2008
- 7.62 x 39 image by Lee O'Dell from Fotolia.com