Long Range Hunting Online Magazine


Go Back   Long Range Hunting Online Magazine > Rifles, Reloading, Optics, Equipment > Rifles, Bullets, Barrels & Ballistics

Rifles, Bullets, Barrels & Ballistics Applied Ballistics


Reply

Twist Rates and Velocity?

 
LinkBack Thread Tools Display Modes
  #1  
Old 03-11-2013, 12:15 PM
Platinum Member
 
Join Date: May 2008
Location: South of Canada and North of Wyoming
Posts: 5,953
Twist Rates and Velocity?

The question is how much does twist rate affect muzzle velocity? I.e. going from a 10 twist to a 9 twist in a 308 cal rifle.

Is there any differences by cal? I.e. does a faster twist rate in a 7mm slow down a bullet more than in a 308?
__________________
- Mark

You will never know how much it has cost my generation to preserve your freedom. I hope you make good use of it.
~ John Quincy Adams
Reply With Quote
  #2  
Old 03-11-2013, 12:34 PM
Platinum Member
 
Join Date: Oct 2008
Location: Alabama
Posts: 6,084
Re: Twist Rates and Velocity?

Barrel length and twist rate are both contributing factors for velocity. The tighter that twist is, and the longer that barrel is, the longer and faster that bullet starts spinning.... For example, a .308 with 175gr bullets with an 11.25" twist 24" barrel will produce higher velocity and greater accuracy at distance, b/c it won't start tumbling as soon as say a 11.25" 20" barrel...

Yes, all different calibers have different FPS variations depending on twist, barrel length, load data, etc... All the different calibers that use the same diameter bullet all have differences. You have to get VERY specific when it comes to your gun. Every gun is individual. Every gun will shoot different, even if it is 2 identical guns made consecutively by the same gunsmith. It's the nature of the beast.
__________________
"I'm just a peckerwood who lives in the hills with too many guns..." - Bob Lee Swagger

"Give me a minute...I'm good. Give me an hour...I'm great. Give me 6 months...And I'm unbeatable." - Col. Hannibal Smith

Ignore everything I say, because I have a reading comprehension and memory problem...

Quote:
Originally Posted by WildRose View Post
The 284 is to the STW what a tricycle is to a Ninja.
Reply With Quote
  #3  
Old 03-11-2013, 01:46 PM
Platinum Member
 
Join Date: May 2008
Location: South of Canada and North of Wyoming
Posts: 5,953
Re: Twist Rates and Velocity?

Quote:
Quote:
Originally Posted by MudRunner2005 View Post
Barrel length and twist rate are both contributing factors for velocity. The tighter that twist is, and the longer that barrel is, the longer and faster that bullet starts spinning.... For example, a .308 with 175gr bullets with an 11.25" twist 24" barrel will produce higher velocity and greater accuracy at distance, b/c it won't start tumbling as soon as say a 11.25" 20" barrel...

Yes, all different calibers have different FPS variations depending on twist, barrel length, load data, etc... All the different calibers that use the same diameter bullet all have differences. You have to get VERY specific when it comes to your gun. Every gun is individual. Every gun will shoot different, even if it is 2 identical guns made consecutively by the same gunsmith. It's the nature of the beast.
Actually barrel length has nothing to with how fast a bullet spins other than longer barrels usually produce more velocity which spin the bullet faster.

My question is for example, how much slower will a barrel with a 9 twist push a bullet then the same type of barrel with a 10 twist pushing the same bullet? 10 fps? 30 fps? 50 fps?
__________________
- Mark

You will never know how much it has cost my generation to preserve your freedom. I hope you make good use of it.
~ John Quincy Adams
Reply With Quote
  #4  
Old 03-11-2013, 02:48 PM
Platinum Member
 
Join Date: Apr 2012
Location: The cold part of Montana
Posts: 1,390
Re: Twist Rates and Velocity?

Given the difference that you can experience from one barrel to next in the same production. How would a guy ever quantify that? When you change barrels your entering a whole new set of controls, so your results are going to be different to a point.
__________________
Keep in mind the animals we shoot for food and display are not bullet proof. Contrary to popular belief, they bleed and die just like they did a hundred years ago. Being competent with a given rifle is far more important than impressive ballistics and poor shootability. High velocity misses never put a steak in the freezer.

Joe
Reply With Quote
  #5  
Old 03-11-2013, 02:57 PM
Platinum Member
 
Join Date: May 2008
Location: South of Canada and North of Wyoming
Posts: 5,953
Re: Twist Rates and Velocity?

Yeah Joe, I figured it would be a tough question. But comparing apples to apples, same make and type barrel I'm wondering if anyone has any experience or a good idea of the difference.
__________________
- Mark

You will never know how much it has cost my generation to preserve your freedom. I hope you make good use of it.
~ John Quincy Adams
Reply With Quote
  #6  
Old 03-11-2013, 03:34 PM
Silver Member
 
Join Date: May 2009
Location: Prosperity, Pa
Posts: 373
Re: Twist Rates and Velocity?

I agree that it would be hard to quantify a different velocity, the faster spin will stabilize longer and heavier bullets. They go slower because they are heavier. The only reason for the faster twist is to stabilize. I have a 22-243 with a 7 twist that shoots 80g bergers quite well but if I shoot 52 g bullets, some spin apart before getting to the target.
__________________
Phil Conklin.... Shooting Instructor for The Best of the West
Reply With Quote
  #7  
Old 03-11-2013, 03:53 PM
Platinum Member
 
Join Date: Oct 2008
Location: Alabama
Posts: 6,084
Re: Twist Rates and Velocity?

Quote:
Originally Posted by MontanaRifleman View Post
Actually barrel length has nothing to with how fast a bullet spins other than longer barrels usually produce more velocity which spin the bullet faster.

My question is for example, how much slower will a barrel with a 9 twist push a bullet then the same type of barrel with a 10 twist pushing the same bullet? 10 fps? 30 fps? 50 fps?
You misunderstood....The bullet SPINS faster from a longer barrel BECAUSE there is more time it is touching the rifling and being acted upon by the rifling force for stabilization purposes. The rifling actually slows the bullet down slightly other than if it were a smooth-bore gun, b/c the rifling is actually biting into the bullet's jacket. So rifling has a very very miniscule affect on the velocity.
__________________
"I'm just a peckerwood who lives in the hills with too many guns..." - Bob Lee Swagger

"Give me a minute...I'm good. Give me an hour...I'm great. Give me 6 months...And I'm unbeatable." - Col. Hannibal Smith

Ignore everything I say, because I have a reading comprehension and memory problem...

Quote:
Originally Posted by WildRose View Post
The 284 is to the STW what a tricycle is to a Ninja.
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes



All times are GMT -5. The time now is 10:56 PM.


Powered by vBulletin ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Management Powered by vBadvanced CMPS
All content ©2010-2014 Long Range Hunting, LLC