Rifle Twist 101: A Basic Understanding

When looking to buy a new rifle or build one of your own, one of things to look at is rifle twist. This is a characteristic of the barrel that will affect how your bullets perform down range and, to some degree, will dictate what rounds should be fired out of that weapon. Rifle twist is expressed as a ratio. An example would be a 1/7 or 1:7 twist. This means that for every seven inches of barrel, there will be one complete twist or rotation of the rifling, which imparts spin onto the bullet. Without getting too in depth about bullet types, this should explain the basics of how rifle twist influences bullet flight and what a buyer should look for to fit their own needs.

The rifling of the barrel causes a bullet to spin. This spin is directly related to how “tight” or “loose” the rifling in the barrel is. Faster spins are good for longer bullets as they need more spin to stabilize their center of gravity. Often times, shooters choose tighter twist rates for heavier bullets. This can make shooters think that it is the weight of the bullet that requires a certain twist rate. This is not (entirely) true. To make a bullet heavier, the bullet is made longer to add material without increasing caliber. It is this length that needs the twist rate.

RiflingEarly M16s used a 1:14 twist rate as they fired light and short bullets. This rate was very limited in what it could do; not even the 55 grain rounds used were spinning fast enough. The military then moved up to 1:12 twist that put a better spin on the bullet. As heavier rounds came out, the twist rate became tighter and tighter. The 1:9, the military found, was good still slow enough for the 55 grain rounds, but it was fast enough for 75 grain bullets as well. As barrels became shorter however, it was noted that even tighter twist rates were needed. This was because a bullet needs at least two rotations in the barrel to become stable. A 16 inch barrel with a 1:9 twist cannot deliver this, so the twist rate was tightened to 1:8. As barrels became even shorter and bullets became heavier, twist rates were again increased. During testing however, it was noted that bullets that twisted too fast could tear themselves apart if the copper jacket had any imperfections. For this reason, the 10.5 inch barrels on AR15s still use a 1:7, sacrificing a full two rotations in order to not over spin the round and cause it to break apart.

With that little history lesson, we can start to see what is needed for our rifle barrels. If you plan to use a rifle for varmint hunting loaded with 45 grain rounds, you are going to want a slow twist rate. If the purpose of the rifle is to have heavy hitting rounds at 300 meters and will be loaded with 70 grain rounds, a twist rate of 1:7 will do better. By matching the proper twist rate to the proper rounds, you can ensure that you will fire stable rounds that will give the most accuracy your rifle has to offer.

Disclaimer: The content in this article is the opinion of the writer and does not necessarily reflect the policies or opinions of US Patriot Tactical.

Seth Belt

Seth grew up in Southern Arizona before joining the U.S. Navy. While serving in the Navy, Seth was an anti-narcotics operator and an anti-submarine operator for 5 years. He was lucky enough to travel to many of the Central and South American countries, as well as visiting many South East Asian nations and islands. One of Seth’s greatest joys from his time in the Navy was teaching new Sailors firearms education and safety. After leaving the Navy in 2010, Seth returned to Arizona and had a rough time learning how to be a civilian again, often working jobs that could barely pay the bills. After going to school, Seth became an Emergency Medical Technician in the Phoenix Valley, where he now lives with his wife and son.His areas of knowledge cover military, firearms, and emergency medicine.
Seth Belt
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2 thoughts on “Rifle Twist 101: A Basic Understanding

  1. Good informative article. My only criticism is that the only negative consequence of too high a rate of twist the author mentioned was bullet failure.

    A higher rate of rifling “twist” then what is required to stabilize a bullet has other negative consequences. As the rate of twist increases so does barrel wear, friction and chamber pressure. Energy is required to spin a bullet faster. So, as rate of twist increases bullet velocity slightly decreases, all else being equal. And finally, as rate of twist increases the effects of bullet imperfections are magnified, decreasing accuracy. Ever have a car tire out of balance? The faster you drive, the more the car vibrates.

    Shooters interested in the highest possible degree of accuracy, such as competitive benchrest shooters, usually prefer to have the slowest rates of twist that will stabilize a given bullet length (weight) to the distances at which they are being fired. More is not always better.

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