Originally Posted by 80 grains
I am wondering why it says on the box of Sierra 180 gr hpbt 8" twist or faster?
Bullets require a certain spin rate to stabilize them in flight. A general rule of thumb is, the heavier (usually longer) the bullet the faster it will need to be spun to stabilize it. The Sierra 180gr you speak of, the manufacturer is recommending 1-8" twist in the barrel as a minimum requirement.
The lower the number, the faster the twist.
1-12 is a slower twist rate than 1-10 for example.
This means in a 1-12" barrel, the bullet will be turned 1 full revolution in 12" of barrel travel. A 1-8" it happens in 8"
Hope that helps.