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What Does A Barrel's Twist Rate Mean...

I wish that the video also didn't propagate the blind-faith of "faster-twist = 'heavier' (longer)."

The quality and construct of the cartridge and projectile always has a say in how well things go (and here, the video also propagates the myth that somehow "green tips" are supposed to be magically better than "white box junk"), and there's always the chance that the shooter's unique carbine/rifle, as a matter of tolerance variations, may perform inconsistently versus this dogma.

Instead of going into terminal ballistics, he could've stuck to the topic better, and offered a more complete/accurate portrait - which, luckily, many of the comments below the video picked up on and addressed.
 
My story on twist rate.
Two rifles
1. Remington 700 heavy barrel 20" barrel 1:12 twist
2. Eagle Arms AR 15 heavy barrel 20" barrel 1:9 twist

Same 1/2" metal plate both guns shot fmj 5.56
Remington you could see lead splatter no hole
Eagle arms AR bored a hole 1/2 way through. The hole looked like something exploded out of the hole. Ragged sharp volcano like look.
Both shot from a bench 80yrds away.
My take away is faster twist stabilization caused it to bore into metal instead of like the Remington just making a lead mark on the plate.
Plate diameter 16" did not shoot at the same location. Plate had not been shot at before this test. Plate was drilled and bolted into old large telephone stacked back stop. Plate had no swing or movement.
After test plate was hung from tree with chains.

I don't buy the "over stabilization yaw" he tried to explain. In my experience over stablize a bullet it comes apart mid air. I was always under the impression that any bullet spun too fast will eventually come apart (explode) mid air.
I've read about this many time with folks using the wrong bullets with fast rifling in varmit cartridges.
 
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Pitdogg2 said:
My story on twist rate.
Two rifles
1. Remington 700 heavy barrel 20" barrel 1:12 twist
2. Eagle Arms AR 15 heavy barrel 20" barrel 1:9 twist

Same 1/2" metal plate both guns shot fmj 5.56
Remington you could see lead splatter no hole
Eagle arms AR bored a hole 1/2 way through. The hole looked like something exploded out of the hole. Ragged sharp volcano like look.
Both shot from a bench 80yrds away.
My take away is faster twist stabilization caused it to bore into metal instead of like the Remington just making a lead mark on the plate.
Plate diameter 16" did not shoot at the same location. Plate had not been shot at before this test. Plate was drilled and bolted into old large telephone stacked back stop. Plate had no swing or movement.
After test plate was hung from tree with chains.

I don't buy the "over stabilization yaw" he tried to explain. In my experience over stablize a bullet it comes apart mid air. I was always under the impression that any bullet spun too fast will eventually come apart (explode) mid air.
I've read about this many time with folks using the wrong bullets with fast rifling in varmit cartridges.
Click to expand...
I suspect the 1:12 wasn’t stabilizing the bullet to the point it was “keyholing” and striking the gong while yawing.
 
HansGruber said:
I suspect the 1:12 wasn’t stabilizing the bullet to the point it was “keyholing” and striking the gong while yawing.
Click to expand...
Nope.
Put the same rounds on paper and it make very precise round bullet holes. I've shot many many varmits and coyotes with this Remington 700. They would dispute that the bullet at 200 yrds was tumbling. It makes nice little smaller than a dime hole with 10 shots off a bench. The most accurate tack driving rifle I've ever had. It's former life was swat sniper weapon. They put a very nice 3oz trigger on it.
It's legit!
I put a nice BSA catseye scope on it many years ago and zeroed it at 150yrds.
Although I was shooting white box 5.56 through it and it is listed as .223, I called Remington 20+yrs ago to check. They told me the Remington heavy barrel varmit synthetic was perfectly ok shooting 5.56 and not to worry about it.
Does it get a steady diet of 5.56 absolutely not.

It shoots 40 and 55 grain bullets excellent, it does not group worth a hoot with heavier bullets in the 70+ grain. I will give you that
 
I was under the impression that rate of twist was so you could used specific heavier grain bullets. I have a Colt MT6700 and the rate of twist I believe is 1 in 9. It is supposed to be for shooting the heavier grain bullets. To say this is the best twist is like asking what is best for hunting? Well are you hunting field mice or pissed off grizzly bear? Specifics matter.And Pitdogg2 what grain bullets do you shoot?
 
What needs too be tested is barrel length vs velocity vs bullet weight/length. Some of the heavier lower velocity won't stabilize enough even at 100 yards. Many factors are needed too be known when you decide on what this gun could be used for. With the m4 at 14.5" w/7 twist some state that it over stabilizes a 62gr bullet. What can happen is that at the longer distances the rpm will slow down enough for it too yaw thus the 7 twist comes to play. An 8 or 9 twist will stabilize fine, but can unyielding for the m4. Plus when they decide to chamber 77gr it becomes a no brainer!
 
cico7 said:
Does a faster twist slow the bullet speed on the same length barrel? I am thinking more friction on the projectile as it travels the barrel.
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benstt said:
I can see that being a reasonable theory. Faster twist would mean more time in contact with the ID of the barrel and more friction. I can't speak to the amount that actually matters.
Click to expand...
What it can cause for the reloader is if a barrel (both being say 20") 11 twist and the velocity has reached peak chamber pressure it can cause higher pressure in a faster twist! Not really slowing it down, but causing the need for less powder of the same burn rate (example IMR4831). That in turn will reduce the velocity.
 
USAFA TWINS DAD said:
I was under the impression that rate of twist was so you could used specific heavier grain bullets. I have a Colt MT6700 and the rate of twist I believe is 1 in 9. It is supposed to be for shooting the heavier grain bullets. To say this is the best twist is like asking what is best for hunting? Well are you hunting field mice or pissed off grizzly bear? Specifics matter.And Pitdogg2 what grain bullets do you shoot?
Click to expand...
It's not about what people think or opinion about it, just what is required enough too stabilize! Gerrnhill is an older version, but still can work. JBM Ballistics is an updated version that used an extra stability factor. If you know the bullets specs you can go online and check using the stability calculator.
 
Pitdogg2 said:
Nope.
Put the same rounds on paper and it make very precise round bullet holes. I've shot many many varmits and coyotes with this Remington 700. They would dispute that the bullet at 200 yrds was tumbling. It makes nice little smaller than a dime hole with 10 shots off a bench. The most accurate tack driving rifle I've ever had. It's former life was swat sniper weapon. They put a very nice 3oz trigger on it.
It's legit!
I put a nice BSA catseye scope on it many years ago and zeroed it at 150yrds.
Although I was shooting white box 5.56 through it and it is listed as .223, I called Remington 20+yrs ago to check. They told me the Remington heavy barrel varmit synthetic was perfectly ok shooting 5.56 and not to worry about it.
Does it get a steady diet of 5.56 absolutely not.

It shoots 40 and 55 grain bullets excellent, it does not group worth a hoot with heavier bullets in the 70+ grain. I will give you that
Click to expand...
A 1/12 is way too slow for 70 grainers.
 
Pitdogg2 said:
My story on twist rate.
Two rifles
1. Remington 700 heavy barrel 20" barrel 1:12 twist
2. Eagle Arms AR 15 heavy barrel 20" barrel 1:9 twist

Same 1/2" metal plate both guns shot fmj 5.56
Remington you could see lead splatter no hole
Eagle arms AR bored a hole 1/2 way through. The hole looked like something exploded out of the hole. Ragged sharp volcano like look.
Both shot from a bench 80yrds away.
My take away is faster twist stabilization caused it to bore into metal instead of like the Remington just making a lead mark on the plate.
Plate diameter 16" did not shoot at the same location. Plate had not been shot at before this test. Plate was drilled and bolted into old large telephone stacked back stop. Plate had no swing or movement.
After test plate was hung from tree with chains.

I don't buy the "over stabilization yaw" he tried to explain. In my experience over stablize a bullet it comes apart mid air. I was always under the impression that any bullet spun too fast will eventually come apart (explode) mid air.
I've read about this many time with folks using the wrong bullets with fast rifling in varmit cartridges.
Click to expand...
With some bullet design it's more about "will it stay together"! You can't really over stabilize, just rev them up too much! Thin jacket bullets will/can come apart, but all copper can handle the high rpm.

http://bulletin.accurateshooter.com/2008/06/calculating-bullet-rpm-spin-rates-and-stability/
 
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