Don't Get Your Panties In A Twist!!

OVER BARREL TWIST, THAT IS.

The last few days,  I have been getting  a lot of questions about barrel twist ratios particularly AR 15 rifles.

Here is my attempt to explain barrel twist in a not so technical manner.

First, there are two kinds of rifle barrels:

Smooth bore and Rifled.

What is a Smooth bore barrel?

   A smooth bore barrel is completely round and smooth on the inside of the barrel.  A good example would be a canon on a pirate ship or in most shot guns.

What is a Rifled barrel?

  A Rifled barrel,  has small  grooves inside the barrel, called Rifling.   What is rifling? The grooves inside the barrel make the projectile spin, which makes the projectile stabilize. Which means more accuracy.

Now that you understand rifling, let's get into rate of twist.

 Rate of twist is measured in inches.  Example  1:9  = 1 complete  revolution  in 9 inches. So, a rifle with a 1:9 twist, means the projectile  has to travel 9 inches to make 1 full turn.  A 1:12 twist barrel, means the projectile  has to travel 12 inches to make 1 full turn.  1:7, 1:8, 1:10, etc..... you get the point.


Are you asking yourself "What the heck does all this stuff mean?"  I will  break it down for you.

1:7 is a fast twist
1:14 is a slow twist
1:9 is a compromise between the both


Confused yet?

1:7 twist will stabilize a 62gr and higher bullet best
1:14 twist best stabilizes a 55gr and under best
1:9 twist will stabilize anything up to 70gr best
There are many more twist out there (I am using these 3 for this example)
I am using an AR 15 in 5.56 for this example.

It is possible to over-stabilize and under-stabilize

over-stabilize; light bullet in a fast twist barrel.  The projectile can disintegrate or fly with the the nose of the round pointing up. Affecting accuracy.

under-stabilize; heavy bullet in a short twist barrel. The bullet will fly through the air sideways. Again, affecting accuracy.

*Rule of Thumb*

• Bullet weight influences length
• The longer the bullet, the faster the twist needed

Remember:      Different caliber rifles require different twist.

For 95% of AR 15 owners 1:9 twist is more than good enough for the shooting they do.  Unless you are shooting Varmints then you would want a slower twist (1:14), or if you want heavy bullets at long range (1:7) would be a better choice.

Check the manufactures recommendations for bullet grains and twist rate, and find the one that best suits you!