Precision Fundamentals: Engineering AR-15 Accuracy

Precision shooting is an engineering discipline. The variables that determine group size and point-of-impact consistency can be analyzed, measured, and systematically optimized. Understanding the physics of barrel harmonics, projectile stability, and system consistency is the foundation of building and operating a precision rifle.

Barrel harmonics — the vibration pattern of the barrel during firing — determine where the muzzle is pointing when the projectile exits. A free-floating barrel eliminates stock contact as a variable. Consistent ammunition produces consistent harmonic excitation. A well-matched barrel-ammunition system exits the projectile at a node of the harmonic wave, reducing the sensitivity of group size to small variations in velocity. Related: Chamber, Twist Rates, and Bullet Selection | Gas Port Erosion and SD/ES