GBullet
09-04-2004, 01:30 AM
When I talk about firearm safety with someone new to shooting, I refer to the danger as a line extending straight out from the muzzle. I know that this is technically wrong, but they would likely roll their eyes if I called it an arced, overstabilized helix.
When you fire your a gun, the bullet wants to exit the muzzle in a straight line. As the bullet emerges, random variables such as the irregular escape of the propellant gases, bullet imperfections and the absence of the barrel to guide it, cause the bullet to wobble. This wobble, or yaw, makes the air flowing around the bullet to push it in the direction of yaw. Due to gyroscopic forces, a spinning bullet will try to move sideways to the direction that it is pushed. As the bullet starts to move, the process repeats itself, leading the bullet to fly in a spiral path. Many factors come together to settle the bullet into a steady spiral. The spiral is usually of such a small diameter that it's ignored, but it is there.
As the bullet proceeds toward the target, the nose is asked to turn downward to continuously point in the direction of travel. If the bullet has the minimum spin to stabilize it, the nose should gently turn to point in the direction of travel as gravity pulls the bullet earthward. However, if the bullet is spun too fast it will resist this change, resulting in yaw, spiral and drift more than necessary. The yawing will slow the bullet far more quickly than zero-yaw. The spiral will also grow more pronounced, yielding inconsistent groups. Yes, bad things happen when you spin the bullet too fast or too slow.
Modern rifle bullets almost always leave the muzzle at a speed faster than sound. High velocity has many virtues for a rifle bullet. As the rifle bullet flies through the air, it slows. At some distance, the rifle bullet will have slowed to slightly faster than the speed of sound. When this happens, some of the shock waves emanating from the bullet begin to shift fore and aft. Vibrations set in and the bullet begins to wobble, thus accentuating accuracy problems. For this reason .22LR target shooters use subsonic ammo and precision rifle shooters try to maintain supersonic velocity of their bullet until it reaches the target.
So, when someone tells you that the bullet flew straight from the rifle to the target...they lied. ;)
When you fire your a gun, the bullet wants to exit the muzzle in a straight line. As the bullet emerges, random variables such as the irregular escape of the propellant gases, bullet imperfections and the absence of the barrel to guide it, cause the bullet to wobble. This wobble, or yaw, makes the air flowing around the bullet to push it in the direction of yaw. Due to gyroscopic forces, a spinning bullet will try to move sideways to the direction that it is pushed. As the bullet starts to move, the process repeats itself, leading the bullet to fly in a spiral path. Many factors come together to settle the bullet into a steady spiral. The spiral is usually of such a small diameter that it's ignored, but it is there.
As the bullet proceeds toward the target, the nose is asked to turn downward to continuously point in the direction of travel. If the bullet has the minimum spin to stabilize it, the nose should gently turn to point in the direction of travel as gravity pulls the bullet earthward. However, if the bullet is spun too fast it will resist this change, resulting in yaw, spiral and drift more than necessary. The yawing will slow the bullet far more quickly than zero-yaw. The spiral will also grow more pronounced, yielding inconsistent groups. Yes, bad things happen when you spin the bullet too fast or too slow.
Modern rifle bullets almost always leave the muzzle at a speed faster than sound. High velocity has many virtues for a rifle bullet. As the rifle bullet flies through the air, it slows. At some distance, the rifle bullet will have slowed to slightly faster than the speed of sound. When this happens, some of the shock waves emanating from the bullet begin to shift fore and aft. Vibrations set in and the bullet begins to wobble, thus accentuating accuracy problems. For this reason .22LR target shooters use subsonic ammo and precision rifle shooters try to maintain supersonic velocity of their bullet until it reaches the target.
So, when someone tells you that the bullet flew straight from the rifle to the target...they lied. ;)