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How to Find Out What Twist My AR 15 Barrel Is?

Gun barrels have what is known as a rifling twist rate. Rifling twist rates are used to calculate the optimum bullet weight for a specific caliber gun and the speed of that bullet by properly spinning the bullet. A proper spinning bullet will not yawn and pitch while traveling down the barrel. AR-15 rifle owners who do not know what twist rate their barrel has can determine that barrel's actual twist rate themselves by examining the barrel or calculating the rate.

Things You'll Need

Cleaning rod
Marker
Cleaning patch

Instructions

- 1
  Ensure that the AR-15 is unloaded and examine the barrel for any numbers. If you see something stamped on the barrel, such as 1:10 or 1:8, then this is that barrel's twist rate.
- 2
  Calculate your AR-15's twist rate if the rate is not stamped on the barrel by making a straight line down your barrel cleaning rod with a marker.
- 3
  Place a cleaning patch on the cleaning rod and put it in the end of the barrel. Make a mark on the cleaning rod at the starting point. Mark a small spot on the barrel as well.
- 4
  Insert the rod slowly into the barrel until you make one revolution, or until the line on the barrel lines up with the line on the cleaning rod. Make another mark on the rod, next to the muzzle.
- 5
  Rotate the rod through the barrel a second time until the lines meet up, and make another mark on the rod. Remove the cleaning rod from the barrel.
- 6
  Measure the marks on the cleaning rod to determine the rifling twist rate of the AR-15's barrel. The distance between the first mark and second will be the second number in the ratio. If you meaure 10 inches, your twist rate is 1:10 and if you measure 13 inches, your twist rate is 1:13.

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