Does the Barrel Twist Rate affect accuracy?

Am Shooting Journal ^ | 9/27/2018 | C Cocoles

[w1n1]

Many of you that are gun geeks understand the basics of rifling can skip this article. This is for the average gun enthusiasts and newbies that enjoy shooting and want a little more understanding of how a barrel twist rate can affect accuracy.
So does barrel twist rate affect accuracy on an AR15?
The short technical answer is that barrel twist starts the bullet spinning at a given rate to stabilize the bullet.
The rate has to be constant for the utmost accuracy.
On the opposite end of the spectrum – Decreasing the twist rate will almost certainly result in a dramatic decrease in accuracy.
Another factor is can the wrong weight of the bullet for your twist rate make it fly off into the sunset? It does matter.

When it comes to slower rifle twist, i.e. 1:14, 1:12, 1:9, you really shouldn't be shooting bullet weights over 65 grains or the equivalent length for a 65-grain bullet.
It won't damage your rifle, but you will have very poor accuracy.
It is true that heavier, longer bullets in the 69-85 grain flavors like faster rifle twists of 1:8, or 1:7.

Here's an experiment that was run a gun enthusiasts, he was trying to see if the AR barrel twist rate really matter, his approach is on a practical level, here's his take on this:

"I experiment with multiple loads of .223 Remington and 5.56 NATO. Ten different loads to be exact. And to make this even more scientific, I did it with two different rifles that both have a 1:7 rifle twist.

The first rifle that I tested is a home-rolled rifle that utilizes a Radical Barrels, LLC 20″ 416R stainless barrel. The second rifle is a factory Bushmaster Minimalist.
Here's the ten different bullets from the lightest grain to heaviest shot:
-Hornady 40 Grain V-Max
-Winchester 45 Grain JHP
-Federal 50 Grain JHP (Varming & Predator)
-Remington UMC 50 Grain JHP
-Tul-Ammo 55 grain FMJ
-Barnes 55 Grain TSX
-Remington 55 Grain PSP
-Barnes 62 Grain TSX
-IMI 77 Grain OTM Razorcore
-Barnes 85 Grain OTM
Read the rest of this test on barrel twist rate.

[mountainlion]

Calculate the RPM of a bullet coming out of a barrel for a big surprise.

[ZULU]

There are many factors involved like ballistic coefficient, size of projectile, speed of projectile, weight of projectile, etc.
For instance, round ball rifles need a slow twist for maximum accuracy while mini- ball rifles need a faster twist and modern smokeless powder needs faster twists.

They even fool around with types of rifling and things like gain twists.

The complexity makes it interesting.

[gundog]

For simplicity, stick with a 1:7 rifling twist. That’s his conclusion? Meh...I just came for the grammatical errors.

[dmcnash]

And calculate the energy due to the spin

[Centurion2000]

Match the bullet weight to twist rate for best accuracy.

Faster twists use heavier bullets in that particular caliber.

[Dalberg-Acton]

Anyone who has thrown a football should understand some of the basics of spin stabilization. Not enough spin for the weight and speed makes the football wobble or go end over end. Too much spin and the ball won’t follow the leading point in its flight. Instead, it will remain at whatever angle, in reference to the ground, it began with througout its flight.

[Erik Latranyi]

If you want complexity, consider the cartridge shape, volume, amount of powder, burn rate of powder, etc to understand the combustion chamber effects created by those variables!

It is fascinating stuff!

If you want something to ponder, consider the Ackley Improved cartridges and the reason they generate higher velocities than their conventional root cartridges.

The short answer is that the 45 degree “shoulders” create a more efficient combustion chamber.

It is also known that the more full a cartridge is with powder, the better....providing you do not exceed safe pressures!

Extremely low volumes of powder to cartridge volume have been known to create extreme pressure situations including ruptured barrels!

Despite what I wrote, the science behind cartridge shape, volume, amount of powder, etc is not well understood.

The next real science is in this area as rifling, BC, etc are all well understood.

[mountainlion]

And calculate the energy due to the spin

I remember physics class where we were supposed to calculate the amount of heat generated when a bullet hit a block of wood. I never got that right.

[Yo-Yo]

Want even more surprises, calculate the RPM of a bullet coming out of a 16” and a 20” barrel, both with the same twist rate.

[Fido969]

At extremes, compare a spiral football pass with a knuckleball.

[Red Badger]

Just looking at it from a physics standpoint, I’d say yes, but only at a distance that requires more energy that is diminished by the amount of energy in the spin rate................

[Red Badger]

Brady Vs. Kaepernick.......................

[IYAS9YAS]

Brady Vs. Kaepernick.......................

That'd be spiral vs. knucklehead...

[Dalberg-Acton]

Exactly. Also a ball with too much spin descends with the leading point too high. The ball should follow the point.

[Red Badger]

LOL!............yes!...................

[Big Red Badger]

W1N1 daily trivia,

[TheNext]

Just get a rifle that shoots 1 mile with accuracy.

[Hot Tabasco]

The complexity makes it interesting.

Last weekend I spoke with my nephew's father in law who is retired and moved to mid Michigan and took up competitive bench rest shooting.

I was amazed at how complex the competition level is, especially when it comes to powder charges, shell casings, and tons of other stuff.

Fortunately for him, where he shoots there are several old timers who have been national champions and they have taken him under their wing and have been mentoring him........

[Delta 21]

"Many of you that are gun geeks understand the basics of rifling can skip this article."

Well, they're learnin'. A bit slow, but learnin'.