Dr. John Woods 10.05.20
It is doubtful that you have ever heard your rifle’s barrel make a whiney sound from vibrations as the bullet spins down the lands and grooves to exit the muzzle. Likewise that barrel has probably never visually demonstrated a shake, rattle, and roll from a bullet launch either. But in the mechanics and physics of busting a cap, that bullet rocketing down inside the barrel does make a lot of things hum. That hum is barrel harmonics.
Barrel harmonics is the infinitesimal or immeasurably minute movement that a rifle barrel experiences when a bullet is pushed down the barrel at the explosive igniting of the powder load. Such movement is most often associated with the long barrel of a rifle.
The harmonics movement as often described could be side to side, up and down, or even in a circle rotational type movement. It has also been illustrated as in the whipping of a rope as is popular now in an exercise regime by physical fitness gurus. Though the shooter cannot see or may not even feel these vibrations because the bullet’s movement velocity is so swift, the effect is non-the-less a reality. How much so?
Barrel harmonics does impact a rifle’s accuracy. It has been recognized most by the benchrest shooting fraternity. Shooting long range can show evidence when these variant barrel vibrations cause measurable, however small, bullet hits on a target.
Now that long range shooting for hunting is in current vogue, these barrel disturbances could cause concern when targeting large game animals at extreme distances. There have been some reports of such misses at very long ranges that could not be accounted for in the field. Poor barrel harmonics could be such a cause for such misses.
So, how to counteract it? Several years ago Browning thought enough about it, that they added models with their BOSS (Ballistic Optimizing Shooting System) to provide a way to tune a barrel to an exact load to reduce these harmonics. Adjusting the BOSS according to the supplied chart helped reduce barrel vibrations. Limbsaver also makes two different types of rubber vibration dampeners to slide down a barrel to help reduce barrel whip. These do work.
For average hunting ranges, barrel harmonics is probably not an issue, but it could be at very long ranges. Consider buying rifle barrels of at least medium to heavy weight, not the pencil thin ones. Also think before you buy those 26-inch barrels, as they vibrate more. Barrel harmonics is just one more shooting factor to consider.