AR-15 Barrel Twist Rates

Barrel twist rate requirements are largely determined by projectile length, which generally correlates well to the projectile weight. Below is a table for different barrel twist rates and different weight projectiles. This is a general table and will vary some between different bullets of the same weight but having different geometry.

	40	45	50	55	60	62	65	69	70	75	77	80	85	90
1:16”	I	I	G	G	P	P	P	P	P	P	P	P	P	P
1:14”	I	I	I	G	G	G	P	P	P	P	P	P	P	P
1:12”	G	G	I	I	I	G	G	G	G	P	P	P	P	P
1:10”	P	G	G	I	I	I	I	I	G	G	G	P	P	P
1:9”	P	G	G	G	I	I	I	I	I	G	G	G	G	P
1:8”	P	P	G	G	G	I	I	I	I	I	I	I	G	G
1:7”	P	P	P	G	G	G	I	I	I	I	I	I	I	G
1:6”	P	P	P	P	G	G	G	G	G	I	I	I	I	I

Legend:

I	Ideal - Best twist rate for this bullet weight.
G	Good - Some accuracy lost, but still a very good performer.
P	Poor - Won’t have optimum accuracy due to over/under stabilization of the bullet.

Notes:

• 55 and 62 gr bullets are the most commonly used. For these, 1:7” to 1:9” are commonly used in carbine rifles and work well for general use even though it may not be ideal from an accuracy standpoint.