How to Calculate a Rifle Twist

Muzzle of a rifle barrel

Rifle twist--rifling--refers to the twisting lands and grooves in the barrel of a firearm, specifically, the rate at which those lands and grooves rotate a bullet as it moves through the barrel. Rifle twist is measured as the number of revolutions per number of inches. For example, a 1:10 twist indicates one revolution per 10 inches. It can also be written as 1/10 or stated as one in 10 twist. The name, "rifle," is a derivative of rifling. Shotguns and muzzle loaded guns do not typically have rifling. The science of calculating rifle twist is really no science at all but rather very intuitive.

Things You'll Need

• Cleaning rod
• Scissors
• Expendable t-shit
• Tape measure
• Masking tape
• Pen
• Paper

Instructions

1. Measure the length of your cleaning rod from the eyelet at the end of the rod to the base of the rod's handle. Write that number on the paper.

2. Cut a 1x3-inch patch of cloth out of the t-shirt and slide it into the eye of the cleaning rod distributing 1 and 1/2 inches equally on both sides of the eye.

3. 

   A cleaning rod slides 4 or 5 inches down the barrel of a rifle.

   Slide the end of the rod with the eyelet and cotton patch into the barrel of the firearm four or five inches. The cleaning rod will naturally twist as it slides down the barrel. Stop when the handle of the cleaning rod is perpendicular or horizontal to the firearm's foresight, your choice. If you are measuring the rifle twist of a pistol, only slide the end of the cleaning rod 1/2 to 1 inch into the barrel as you may only have 3 to 6 inches of barrel to work with total.

4. Measure the distance from the base of the rod's handle to the point where the rod enters the barrel of the firearm--the muzzle. Write down the distance. Subtract that number from the total length of the cleaning rod. This difference is equal to the number of inches you have pushed the rod into the barrel.

5. Place your hand on the rod's handle. Twist the handle of the rod--clockwise or counterclockwise, depending on your weapon--one complete 360 degree turn.

6. Measure the distance from the base of the handle to the muzzle of the firearm. Write down that distance. Subtract this second length from the length you originally measured rod to muzzle.

7. Write down the difference and that is your rifle twist rate. If that difference is 7 inches, for example, your firearm has a 1 revolution per 7 inches rifle twist.

Tips & Warnings

• Make certain the patch you uses fits tightly into the muzzle of the barrel. A loose fit will not force the rod to twist as you push it down the barrel.

References

• Barrel Twist Rates
• Rifle Barrel Twist
• Barrel Twist Rate