How to Rifle a Gun

Most gun barrels have rifling on the inside to improve the accuracy of the shot.

Rifling is the set of grooves that spiral along the inside of a gun barrel from one end to the other. Rifling is an important component in all handguns and rifles; it causes the bullet to spin when it is ejected from the muzzle of a firearm to improve the accuracy of the shot. A programmable, deep-hole drilling machine makes a gun barrel from a solid steel rod. The machine first drills a hole through the rod, and then rifling is cut into the bore afterward.

Things You'll Need

• 28-inch rod of heat-treated stainless steel rod
• Deep-hole drilling machine
• Gun drill
• Lubricating oil
• Gun barrel rifling-machine
• Carbide button-rifling tool
• Heat-treatment oven
• Lapping rod
• Molten lead

Instructions

1. Mount the steel rod into the fixture of a deep-hole drilling machine, which spins the steel rod while the gun drill remains in a fixed position. Set the rotation speed of the machine at 4,000 rpm. The machine moves the gun barrel into the drill at a rate of 1 inch per minute.

2. Fill the oil reservoir. The machine pumps lubricating oil through the drill and out a small hole in the tip of the drill bit. Lubrication cools the drill bit and the bored-out hole in the steel rod as the barrel takes shape. The waste oil washes away the steel shavings.

3. Mount the barrel in the cutting box of the rifling machine. Lube the inside of the bore. Attach the carbide button on the end of the drilling rod in the cutting box. The machine will push the carbide button through the barrel using extreme pressure. This procedure forces the shape of the rifling pattern into the surface of the bore without any cutting.

4. Heat-treat the barrel by baking it at 1,112 F with a controlled cool-down cycle. This takes 12 to 24 hours, depending on the properties and grade of steel used to make the barrel. Heat-treating removes the stresses to the gun barrel created by the high pressure of the rifling procedure.

5. Seal the barrel closed by inserting the lapping rod into its back end; this leaves open only the first 4 inches below the muzzle. Pour molten lead into the muzzle to obtain a relief pattern of the rifling; this will be molded into the lap plug when it hardens. Tap out the lap plug and pull it through the barrel with the lap rod and lubrication oil. Pass the lap plug back and forth several times. This polishes the bore and completes the rifling process.

References

• Firearms ID: A Bullet ID Rifling
• LASC: Ranging Shot Barrel Making Feature
• Rifle Barrels: Making Rifle Barrel