What is the twist rate of the M4's rifling?

The M4 carbine features a twist rate of 1/7 right-hand twist, which means that the rifling makes one complete revolution for every 7 inches of barrel length. This specific twist rate is particularly advantageous for stabilizing heavier projectiles, such as the 62-grain M855 and 77-grain Mk 262 rounds, which are commonly used by U.S. forces.

Having a 1/7 twist allows for better long-range accuracy and performance, especially when using ammunition designed for enhanced ballistic performance. The right-hand twist designation indicates the direction of the spiral grooves in the barrel, which is standard in many firearms.

The other twist rates mentioned do not provide the same level of stability for heavier rounds. A 1/9 twist is more versatile for lighter rounds but may not effectively stabilize the heavier ammunition preferred for some tactical situations. Similarly, 1/10 and 1/12 twists are less common in modern military firearms and would likely perform inadequately with heavier bullets, making them less suitable for the M4's intended operational use.