Barrel Twist: What does it mean?
Barrel twist is one of the most commonly misunderstood concepts of firearms. It is insanely important and we highly recommend you understand it before choosing a projectile weight for your rifle.
Rifling is characterized by its twist rate, which indicates the distance the rifling takes to complete one full revolution, such as “1 turn in 10 inches” (1:10 inches or 1-10″). A shorter distance indicates a faster twist, meaning that for a given velocity the projectile will rotate at a higher spin rate.
The combination of length, weight, and shape of a projectile determines the twist rate needed to gyroscopically stabilize it. When an ammunition is listed as needing a 1-9″ barrel minimum, that means that any faster twist will stabilize the projectile as well, 1-8″, 1-7.5″, 1-6″, etc. However, a slower twist like 1-10″, 1-11″, etc. WILL NOT stabilize the projectile and is not recommended or you may have keyholing, where the projectile impacts the target sideways or off axis.
Below is a target where the projectile is not stabilizing. We can see the projectile is striking the target sideways.