Understanding twist rates and bullet stability.


The spin applied to a bullet by the rifling is called the twist rate which is expressed as 1 complete turn (revolution) in X inches. The longer a projectile is the faster it must be spun to stabilize or remain point on in flight. SAAMI has established standard twist rates for most cartridges which are chambered by firearms manufactures. These standard twist rates will stabilize standard for caliber bullet weights. Military and long range target shooters have gone to heavy for caliber bullets to increase ballistic coefficient for extreme long range shooting. These long bullets require faster twist rates in order to properly stabilize. If these heavy for caliber bullets were shot in standard twist-rate barrels, they will wobble or tumble and usually go through the target sideways; also known as “key-holing”.

Last update:
2013-10-31 23:08
Author:
John Bullet
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