Is there a negative side to having too fast of a twist rate?

Deja vu · February 17, 2015, 09:37 AM

I have heard that having too slow of a twist rate can make bullets unstable. Is there any negative to having too fast of a twist rate? I asked at my local gun store (Liars INC

) and they said only that you may loose some velocity.

is that correct? That sounds odd to me.

Bart B. · February 17, 2015, 09:42 AM

The muzzle velocity difference between a fast and slow twist is virtually zero.

But too fast a twist can spin bullets too fast, and, with bullets more unbalanced more than others, the centrifugal forces they have will pull them off the muzzle axis when shot; accuracy gets worse. Which is why competitive shooters use a twist as slow as possible for best accuracy. If the rifling engraves the jacket too much weakening it, the jacket will split and fly off the lead core.

EchoM70 · February 17, 2015, 10:28 AM

I'll also add that a faster twist rate will impact barrel life negatively.

For example; A 1/9 twist .22-250 barrel will have a shorter life than a 1/14 twist barrel.

It's not drastic, but worth noting.

doofus47 · February 17, 2015, 11:27 AM

Doesn't increased twist also affect pressure, by increasing it slightly?
I'm asking, b/c that was an assumption I had picked up from somewhere.

Bart B. · February 17, 2015, 11:53 AM

I have never heard of a faster twist shortening barrel life, increasing pressure or anything else. Nor read any cautions about in any reloading databases. While there may be a little, it's masked by the normal 2 to 3 percent spread across powder charges for a given lot number and charge weight.

A 1:11 twist in a 30 caliber barrel has the same rifling angle to bullets as a 1:8 twist in a 22 caliber one. When a cartridge in each burns 1 grain of powder for each square millimeter of bore cross section area, both have equal barrel lives. .308 Win compared to .222 Rem; 3000 rounds each for best accuracy. A .300 Win Mag with a 1:11 twist barrel lasts about 1200 rounds.

People shooting matches with 155's from a 1:14 twist .308 barrel get the same barrel life as one shooting 240's from a .308 with a 1:8 twist. About 3000 rounds each. Those 240's have a much longer bearing area that's engraved by the rifling than the 155's, but it's the hot, high pressure burning powder that wears out the barrels, not the cupronickel jacketed bullets rubbing the rifling on their way in.

joed · February 17, 2015, 12:50 PM

Bart B is right on. Somewhere I remember seeing a table in relation to this.

A few years ago I picked up a used Savage 10 in .223 to do some groundhog hunting where I live. The rifle had a 1:9 twist.

This was my first faster twist rifle. My first attempt with 50 gr bullets saw groups of 1" at 100 yards. Somehow I just felt the rifle was capable of better.

Second attempt was the Sierra 55 Gr and groups got better, maybe 3/4".

What I found really interesting were the 69 gr Sierra Match bullets, those went into 1 ragged hole.

I spent more time trying lighter bullets in the rifle but I could not duplicate the 69 gr bullets with anything I shot out of it. I've heard others claim they can get very good accuracy out of lighter bullets in a fast twist, I couldn't.

bamaranger · February 17, 2015, 03:43 PM

I have read and heard of folks driving .22 cal slugs , out of long barreled .223 match rifle, , at high velocity, and the bullets just fragment/mist, and the culprit was thought to be a combination of high velocity and twist.

The phrase, as I remember was either ......"he'd shoot an X or a zero".

The other was Hornet slugs driven at 22-250 & Swift velocities, in humid weather, same result.

Bake · February 17, 2015, 04:14 PM

Quote:

But too fast a twist can spin bullets too fast, and, with bullets more unbalanced more than others, the centrifugal forces they have will pull them off the muzzle axis when shot; accuracy gets worse. Which is why competitive shooters use a twist as slow as possible for best accuracy. If the rifling engraves the jacket too much weakening it, the jacket will split and fly off the lead core.

If I remember right, a long long time ago, the bench rest shooters would shoot 308's with a very short & fat barrel with a twist as slow as 16:1 or even 18:1. Of course they changed barrels like most shooters changed sock...

joed · February 17, 2015, 04:22 PM

Just before Winchester announced they were closing the factory I purchased a model 70 Stealth in .308. It is one of my best shooting rifles and I have no complaints. This rifle has the 1:12 twist. Originally I thought I was going to be handicapped with it being limited to 168 gr bullets. But, that hasn't been the case. It will shoot the Berger 185 gr match to 1000 yards just fine. Now, if I were a good shot I'd be even happier.

Twist is something I wish I had more than just a basic understanding of.

Bart B. · February 17, 2015, 04:31 PM

Bake, benchresters shoot the .30 BR round with 110 to 125 grain bullets in 1:17 or 1:18 twist barrels. And the .308 Win will shoot bullets those weights very accurate with the same twist.

Joed, the US Navy and Air Force Rifle Teams used 7.62 NATO Garands shooting Sierra 190's from 24" 1:12 twist barrels. Won a lot of matches with that load shooting against bolt action match rifles shooting new LC M118 match cases and primers with 44 grains of IMR4320. They easily shot sub 2/3 MOA at 600 yards tested from accuracy cradles and a bit over 1 MOA at 1000. I don't think any AR in .308 has shot that well except maybe the Army Team's AR10's with Berger 185's.

Frankford Arsenal knew the old .30-06's 1:10 twist was too fast for best accuracy with 150-gr. bullets, It did better with the 172-gr. FMJBT bullet. When they designed the shorter barreled M14, they chose a 1:12 twist for its 147-gr. ball bullet leaving about 100 fps slower than the 150's did from the .30-06. That M80 round was more accurate in arsenal test barrels than the M2 .30-06 round with 150's ever was.

EchoM70 · February 17, 2015, 05:37 PM

Bart B.

While I don't have any actual data to back up my claim, during my research when constructing a fast twist .22-250 I constantly ran into claims from various forums and other sources that a faster twist will shorten a barrels life with all else equal.

It could be just a myth, but it's one of those things that pops up everytime the conservation comes up.

Bake · February 17, 2015, 05:37 PM

Quote:

Bake, benchresters shoot the .30 BR round with 110 to 125 grain bullets in 1:17 or 1:18 twist barrels. And the .308 Win will shoot bullets those weights very accurate with the same twist

Bart, I was thinking a long time ago, late 60's to early 70's. I shot 7mm BR in the mid 80's...

Bake · February 17, 2015, 06:13 PM

Quote:

While I don't have any actual data to back up my claim, during my research when constructing a fast twist .22-250 I constantly ran into claims from various forums and other sources that a faster twist will shorten a barrels life with all else equal.

Echo, You might want to check out a Savage Mod. 12LRPV (Left Port), I believe it has an 9:1 twist, and I love the Left Port/Right Hand Action. If the barrel will last 6 or 700 rounds, I wouldn't care, because I would have sold or traded it away before then

...

Mobuck · February 17, 2015, 07:55 PM

"Doesn't increased twist also affect pressure, by increasing it slightly?
I'm asking, b/c that was an assumption I had picked up from somewhere."

That is correct but to what extent is hard to prove since variations in bore condition may cause just as much difference between barrels of same twist.

taylorce1 · February 17, 2015, 08:17 PM

In my opinion there is no down side to a fast twist rifle, faster twist opens more doors than a slow twist. I hate being limited on options when it comes to bullets I can use.

Bryan Litz did a test and you can read about it here.

http://bulletin.accurateshooter.com/...ity-litz-test/

There is about a 5 fps difference in velocity between a 12 and 8 twist .308 Win. Without pressure testing equipment to say for sure I'd be willing to bet the pressure increase if any is very minimal.

B.L.E. · February 17, 2015, 10:15 PM

My understanding is that an overstabilized bullet tends to keep its original orientation instead of changing its orientation to align with the air flow like an arrow as the path of the bullet changes in its arcing trajectory. This causes the bullet to fly nose high which reduces its effective BC. The bullets don't keyhole but the accuracy is not optimum.

Bart B. · February 18, 2015, 09:44 AM

I don't think rifle bullets are shot fast enough in a fast twist often, so there's little evidence that bullets spun to fast keep their spin axes at the launch angle throughout their flight exists. There has been some 22 caliber bullets shot over 5000 fps, but I'm not aware of the twist used and maximum range tested at.

The laws of physics for gyroscopes and other spinning things says bullets spun way too fast will keep their launch angle throughout their flight. They'll appear to keyhole going through the target. If launched at an elevation angle of 1 degree, they'll point 1 degree up going through the paper at any down range point. At 1000 yards, it may not show up as a keyhole. The hole it makes in the paper will be elongated vertically less than .001" more than bullet diameter.

Tom Matiska · February 20, 2015, 09:39 PM

If pushing lighter bullets into the photon torpedo range a fast twist will foul a little quicker. Ratio of shooting fun to copper removal goes down. If you solve the copper problem by soaking overnight with harsh solvents barrel life can go down.

Scorch · February 20, 2015, 09:56 PM

Biggest advantage of over-spinning bullets is very high stability in flight. There are several disadvantages, IME. Most notably,
* Bullets take longer to "go to sleep"
* Increased spin drift at longer ranges
* Bullets can spin apart if not well-constructed
* Bullets are more likely to expand violently when hitting game.

B.L.E. · February 20, 2015, 10:43 PM

A link that illustrates the flight of an over stabilized bullet.

http://www.nennstiel-ruprecht.de/bullfly/fig15.htm

**JohnKSa** · February 20, 2015, 11:40 PM

According to Berger, there can be a negative impact on accuracy from spinning a bullet faster than necessary.

http://www.bergerbullets.com/wp_supe...slowest-twist/

"Spinning a bullet faster than necessary can amplify any inconsistency in the bullet. Since we use J4 jackets, you can shoot Berger Bullets in faster twist than what is listed. We list the slowest twist rate needed because we want to squeeze every bit of accuracy out of a rifle."

cw308 · February 23, 2015, 02:51 PM

Bart B's first post answered your question, what caliber are you shooting at what distance.

KEYBEAR · February 23, 2015, 03:33 PM

This Rifle is a 223 and has a 1-12 twist and it shoots light bullets better than heavy I shoot 52 and 53 GR. flat base around 2600 fps . For heavyer bullets I would need a 1-9 or even a 1-8 if shooting more than 200 yards .

KEYBEAR · February 23, 2015, 03:38 PM

This Rifle is a 30-06 and shoots 154 gr. very well with a 1-14 twist . If I did shoot heavyer bullets like a 180 GR. I would like maybe a 1-18 twist .

reynolds357 · February 23, 2015, 05:35 PM

I think your numbers are backwards on that 06 there Keybear.

All my custom built rifles are twisted relatively fast. I have seen many negatives to a barrel being twisted too slow, but I have never seen a problem with a barrel being twisted too fast.
When I build a rifle now, I look at the newest Berger tables and twist slightly faster than the rate they call for in the heaviest/longest bullet they make for that diameter.

February 17, 2015, 09:37 AM	#1
Deja vu Senior Member Join Date: March 14, 2010 Location: Border of Idaho & Montana Posts: 2,584	Is there a negative side to having too fast of a twist rate? I have heard that having too slow of a twist rate can make bullets unstable. Is there any negative to having too fast of a twist rate? I asked at my local gun store (Liars INC ) and they said only that you may loose some velocity. is that correct? That sounds odd to me. __________________ Shot placement is everything! I would rather take a round of 50BMG to the foot than a 22short to the base of the skull. all 26 of my guns are 45/70 govt, 357 mag, 22 or 12 ga... I believe in keeping it simple. Wish my wife did as well...

February 17, 2015, 11:27 AM	#4
doofus47 Senior Member Join Date: June 9, 2010 Location: live in a in a house when i'm not in a tent Posts: 2,483	Doesn't increased twist also affect pressure, by increasing it slightly? I'm asking, b/c that was an assumption I had picked up from somewhere. __________________ I'm right about the metric system 3/4 of the time.

February 17, 2015, 11:53 AM	#5
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	I have never heard of a faster twist shortening barrel life, increasing pressure or anything else. Nor read any cautions about in any reloading databases. While there may be a little, it's masked by the normal 2 to 3 percent spread across powder charges for a given lot number and charge weight. A 1:11 twist in a 30 caliber barrel has the same rifling angle to bullets as a 1:8 twist in a 22 caliber one. When a cartridge in each burns 1 grain of powder for each square millimeter of bore cross section area, both have equal barrel lives. .308 Win compared to .222 Rem; 3000 rounds each for best accuracy. A .300 Win Mag with a 1:11 twist barrel lasts about 1200 rounds. People shooting matches with 155's from a 1:14 twist .308 barrel get the same barrel life as one shooting 240's from a .308 with a 1:8 twist. About 3000 rounds each. Those 240's have a much longer bearing area that's engraved by the rifling than the 155's, but it's the hot, high pressure burning powder that wears out the barrels, not the cupronickel jacketed bullets rubbing the rifling on their way in. Last edited by Bart B.; February 17, 2015 at 03:27 PM.

February 17, 2015, 03:43 PM	#7
bamaranger Senior Member Join Date: October 9, 2009 Location: North Alabama Posts: 8,312	too fast I have read and heard of folks driving .22 cal slugs , out of long barreled .223 match rifle, , at high velocity, and the bullets just fragment/mist, and the culprit was thought to be a combination of high velocity and twist. The phrase, as I remember was either ......"he'd shoot an X or a zero". The other was Hornet slugs driven at 22-250 & Swift velocities, in humid weather, same result.

February 17, 2015, 04:31 PM	#10
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	Bake, benchresters shoot the .30 BR round with 110 to 125 grain bullets in 1:17 or 1:18 twist barrels. And the .308 Win will shoot bullets those weights very accurate with the same twist. Joed, the US Navy and Air Force Rifle Teams used 7.62 NATO Garands shooting Sierra 190's from 24" 1:12 twist barrels. Won a lot of matches with that load shooting against bolt action match rifles shooting new LC M118 match cases and primers with 44 grains of IMR4320. They easily shot sub 2/3 MOA at 600 yards tested from accuracy cradles and a bit over 1 MOA at 1000. I don't think any AR in .308 has shot that well except maybe the Army Team's AR10's with Berger 185's. Frankford Arsenal knew the old .30-06's 1:10 twist was too fast for best accuracy with 150-gr. bullets, It did better with the 172-gr. FMJBT bullet. When they designed the shorter barreled M14, they chose a 1:12 twist for its 147-gr. ball bullet leaving about 100 fps slower than the 150's did from the .30-06. That M80 round was more accurate in arsenal test barrels than the M2 .30-06 round with 150's ever was. Last edited by Bart B.; February 17, 2015 at 04:40 PM.

February 17, 2015, 09:42 AM	#2
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	The muzzle velocity difference between a fast and slow twist is virtually zero. But too fast a twist can spin bullets too fast, and, with bullets more unbalanced more than others, the centrifugal forces they have will pull them off the muzzle axis when shot; accuracy gets worse. Which is why competitive shooters use a twist as slow as possible for best accuracy. If the rifling engraves the jacket too much weakening it, the jacket will split and fly off the lead core.

February 17, 2015, 10:28 AM	#3
EchoM70 Member Join Date: April 4, 2012 Posts: 65	I'll also add that a faster twist rate will impact barrel life negatively. For example; A 1/9 twist .22-250 barrel will have a shorter life than a 1/14 twist barrel. It's not drastic, but worth noting.

February 17, 2015, 12:50 PM	#6
joed Senior Member Join Date: November 28, 2014 Posts: 442	Bart B is right on. Somewhere I remember seeing a table in relation to this. A few years ago I picked up a used Savage 10 in .223 to do some groundhog hunting where I live. The rifle had a 1:9 twist. This was my first faster twist rifle. My first attempt with 50 gr bullets saw groups of 1" at 100 yards. Somehow I just felt the rifle was capable of better. Second attempt was the Sierra 55 Gr and groups got better, maybe 3/4". What I found really interesting were the 69 gr Sierra Match bullets, those went into 1 ragged hole. I spent more time trying lighter bullets in the rifle but I could not duplicate the 69 gr bullets with anything I shot out of it. I've heard others claim they can get very good accuracy out of lighter bullets in a fast twist, I couldn't.

February 17, 2015, 04:22 PM	#9
joed Senior Member Join Date: November 28, 2014 Posts: 442	Just before Winchester announced they were closing the factory I purchased a model 70 Stealth in .308. It is one of my best shooting rifles and I have no complaints. This rifle has the 1:12 twist. Originally I thought I was going to be handicapped with it being limited to 168 gr bullets. But, that hasn't been the case. It will shoot the Berger 185 gr match to 1000 yards just fine. Now, if I were a good shot I'd be even happier. Twist is something I wish I had more than just a basic understanding of.

February 17, 2015, 05:37 PM	#11
EchoM70 Member Join Date: April 4, 2012 Posts: 65	Bart B. While I don't have any actual data to back up my claim, during my research when constructing a fast twist .22-250 I constantly ran into claims from various forums and other sources that a faster twist will shorten a barrels life with all else equal. It could be just a myth, but it's one of those things that pops up everytime the conservation comes up.

February 17, 2015, 07:55 PM	#14
Mobuck Junior member Join Date: February 2, 2010 Posts: 6,846	"Doesn't increased twist also affect pressure, by increasing it slightly? I'm asking, b/c that was an assumption I had picked up from somewhere." That is correct but to what extent is hard to prove since variations in bore condition may cause just as much difference between barrels of same twist.

February 17, 2015, 08:17 PM	#15
taylorce1 Senior Member Join Date: November 18, 2005 Location: On the Santa Fe Trail Posts: 8,249	In my opinion there is no down side to a fast twist rifle, faster twist opens more doors than a slow twist. I hate being limited on options when it comes to bullets I can use. Bryan Litz did a test and you can read about it here. http://bulletin.accurateshooter.com/...ity-litz-test/ There is about a 5 fps difference in velocity between a 12 and 8 twist .308 Win. Without pressure testing equipment to say for sure I'd be willing to bet the pressure increase if any is very minimal. __________________ NRA Life Member

February 17, 2015, 10:15 PM	#16
B.L.E. Senior Member Join Date: December 20, 2008 Location: Somewhere on the Southern shore of Lake Travis, TX Posts: 2,603	My understanding is that an overstabilized bullet tends to keep its original orientation instead of changing its orientation to align with the air flow like an arrow as the path of the bullet changes in its arcing trajectory. This causes the bullet to fly nose high which reduces its effective BC. The bullets don't keyhole but the accuracy is not optimum. __________________ Hanlon's Razor "Do not invoke conspiracy as explanation when ignorance and incompetence will suffice, as conspiracy implies intelligence and organization."

February 18, 2015, 09:44 AM	#17
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	I don't think rifle bullets are shot fast enough in a fast twist often, so there's little evidence that bullets spun to fast keep their spin axes at the launch angle throughout their flight exists. There has been some 22 caliber bullets shot over 5000 fps, but I'm not aware of the twist used and maximum range tested at. The laws of physics for gyroscopes and other spinning things says bullets spun way too fast will keep their launch angle throughout their flight. They'll appear to keyhole going through the target. If launched at an elevation angle of 1 degree, they'll point 1 degree up going through the paper at any down range point. At 1000 yards, it may not show up as a keyhole. The hole it makes in the paper will be elongated vertically less than .001" more than bullet diameter. Last edited by Bart B.; February 18, 2015 at 09:57 AM.

February 20, 2015, 09:39 PM	#18
Tom Matiska Senior Member Join Date: April 12, 2000 Location: Wilkes-Barre, Pa Posts: 1,029	If pushing lighter bullets into the photon torpedo range a fast twist will foul a little quicker. Ratio of shooting fun to copper removal goes down. If you solve the copper problem by soaking overnight with harsh solvents barrel life can go down. __________________ A gun is like a parachute... when you need one you usually need it pretty bad...

February 20, 2015, 09:56 PM	#19
Scorch Senior Member Join Date: February 13, 2006 Location: Washington state Posts: 15,248	Biggest advantage of over-spinning bullets is very high stability in flight. There are several disadvantages, IME. Most notably, * Bullets take longer to "go to sleep" * Increased spin drift at longer ranges * Bullets can spin apart if not well-constructed * Bullets are more likely to expand violently when hitting game. __________________ Never try to educate someone who resists knowledge at all costs. But what do I know? Summit Arms Services

February 20, 2015, 10:43 PM	#20
B.L.E. Senior Member Join Date: December 20, 2008 Location: Somewhere on the Southern shore of Lake Travis, TX Posts: 2,603	A link that illustrates the flight of an over stabilized bullet. http://www.nennstiel-ruprecht.de/bullfly/fig15.htm __________________ Hanlon's Razor "Do not invoke conspiracy as explanation when ignorance and incompetence will suffice, as conspiracy implies intelligence and organization."

February 20, 2015, 11:40 PM	#21
JohnKSa Staff Join Date: February 12, 2001 Location: DFW Area Posts: 24,992	According to Berger, there can be a negative impact on accuracy from spinning a bullet faster than necessary. http://www.bergerbullets.com/wp_supe...slowest-twist/ "Spinning a bullet faster than necessary can amplify any inconsistency in the bullet. Since we use J4 jackets, you can shoot Berger Bullets in faster twist than what is listed. We list the slowest twist rate needed because we want to squeeze every bit of accuracy out of a rifle." __________________ Do you know about the TEXAS State Rifle Association?

February 23, 2015, 02:51 PM	#22
cw308 Senior Member Join Date: September 2, 2010 Location: Plainview , Long Island NY Posts: 3,863	Bart B's first post answered your question, what caliber are you shooting at what distance.

February 23, 2015, 03:33 PM	#23
KEYBEAR Senior Member Join Date: January 11, 2012 Location: Indiana Posts: 1,059	This Rifle is a 223 and has a 1-12 twist and it shoots light bullets better than heavy I shoot 52 and 53 GR. flat base around 2600 fps . For heavyer bullets I would need a 1-9 or even a 1-8 if shooting more than 200 yards .

February 23, 2015, 03:38 PM	#24
KEYBEAR Senior Member Join Date: January 11, 2012 Location: Indiana Posts: 1,059	This Rifle is a 30-06 and shoots 154 gr. very well with a 1-14 twist . If I did shoot heavyer bullets like a 180 GR. I would like maybe a 1-18 twist .

February 23, 2015, 05:35 PM	#25
reynolds357 Senior Member Join Date: December 10, 2012 Posts: 6,165	I think your numbers are backwards on that 06 there Keybear. All my custom built rifles are twisted relatively fast. I have seen many negatives to a barrel being twisted too slow, but I have never seen a problem with a barrel being twisted too fast. When I build a rifle now, I look at the newest Berger tables and twist slightly faster than the rate they call for in the heaviest/longest bullet they make for that diameter.