When measuring twist rate, the rotation being measured is the rotation of which firearm component?

When measuring twist rate, the rotation being measured is the rotation of which firearm component?

• A. Bolt
• B. Rifling
• C. Chamber
• D. Crown

Answer: (B)

Twist rate is about how quickly the barrel’s rifling twists as the bullet travels down the bore. The rotation being measured is the rifling’s rotation around the bore axis—the spiral grooves inside the barrel impart spin to the bullet, and the rate at which those grooves twist is what we call the twist rate. It’s expressed as inches per turn (for example, a 1:8 twist means the rifling completes one full twist every 8 inches of barrel). The bolt, chamber, and crown aren’t responsible for this measured rotation—the bolt locks and unlocks the action, the chamber is fixed, and the crown is simply the muzzle edge. So the correct concept is the rotation of the rifling.

Twist rate is about how quickly the barrel’s rifling twists as the bullet travels down the bore. The rotation being measured is the rifling’s rotation around the bore axis—the spiral grooves inside the barrel impart spin to the bullet, and the rate at which those grooves twist is what we call the twist rate. It’s expressed as inches per turn (for example, a 1:8 twist means the rifling completes one full twist every 8 inches of barrel). The bolt, chamber, and crown aren’t responsible for this measured rotation—the bolt locks and unlocks the action, the chamber is fixed, and the crown is simply the muzzle edge. So the correct concept is the rotation of the rifling.