Twist Rate
The distance, in inches, a bullet travels through the barrel for one full rotation. Written as 1:N. A 1:8 twist makes one full rotation every 8 inches.
Faster twist (lower N) stabilizes longer, heavier bullets. Slower twist works for short, light bullets but won’t stabilize a long heavy projectile at altitude.
A 6.5 Creedmoor in 1:8 will run 140-147 grain bullets all day. The same caliber in 1:10 starts losing 147s past 1,000 yards. Match the twist to the bullets you intend to shoot, then stop fighting your barrel.