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

Fast Twist VS Slow Twist

 
LinkBack Thread Tools Display Modes
  #1  
Old 05-01-2008, 03:40 PM
Platinum Member
 
Join Date: Feb 2005
Location: USA
Posts: 2,598
Fast Twist VS Slow Twist

I have a friend that works in a Ballistics lab and he ran a test with a 223 Rem with a 7 twist and compaired the pressure and velocity to a 14 twist. After runnig the test he told me that the difference in velocity and pressure between the 7 and 14 twist was insignificant.. Many claim that by running a slow twist that they can increase velocity without increaseing pressure, but judging by this test that is not the case. A fast twist barrel can degrade the jackets and cause problems with some bullet, but not all bullets, such as the Barnes TSX bullets..
__________________
range it,check the wind, dial in correction, aim and only one shot
Reply With Quote
  #2  
Old 05-01-2008, 06:11 PM
Platinum Member
 
Join Date: Jun 2007
Location: Wilmington NC
Posts: 4,222
That is certainly interesting.

Cannot wait to see the article discussing it in detail because it certainly flys in the face of practice and experience to say "insignificant velocity and pressure between a 7 and 14 twist". Assuming same load and bullet were used in the same chamber and certainly not a copper solid Barnes.

Until that article is published by Ty and subjected to a little peer review, I will stick with what I have proven to myself by firing the same loads in different twists. Seen too many guys pushing bullets in slow twists at velocities not possible with standard fast twists.

But then maybe I and many others have been wrong all along. Would not be the first time. Guess we will wait for the article.

BH
Reply With Quote
  #3  
Old 05-01-2008, 06:27 PM
Official LRH Sponsor
 
Join Date: Jun 2004
Location: Fort Shaw, Montana
Posts: 6,831
I have had detailed personal conversations with Dan Lilja about this very subject. His feelings were basically the exact same as what your friend told you he saw.

That said, while in a 223 or 308, you will likely not see much difference in pressure or velocity change but when you step up to a chambering that is really extreme, this insignificant change in pressure can become quite significant.

For example, and this is only an example, NOT TRYING TO SELL RIFLES , if I took my 7mm AM with a 160 gr Accubond loaded to 3550 fps, which is a top end practical load, in a 1-10 twist Lilja barrel and then shoot that same exact load in a 1-7 twist Lilja barrel, the faster twist barrel will show obviously higher chamber pressures.

Now if I take that same 7mm AM, load it to 3400 fps and repeat the test, you will hardly notice a difference between the two.

Point being, if you run an extreme round to the red line, you will see MUCH more diffence when small changes are made in things such as bullet weight, twist rate, groove number, groove width and even things such as jacket thickness. In most chamberings these things are pretty much "insignificant" as far as increasing pressure but in extreme performance chamberings, that is not the case.

Another good reason not to load to red line!!!

For conventional chamberings loaded to conventional pressures with conventional weight bullets, I would agree 100%. With the extreme end of chamberings, it can be more noticable when you make changes like this.

Kirby Allen(50)
__________________
Kirby Allen(50)

Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.

Farther, Faster and Flatter then ever before.

Web Page: www.apsrifles.com

allenmagnum@gmail.com
Reply With Quote
  #4  
Old 05-01-2008, 07:05 PM
Platinum Member
 
Join Date: Feb 2004
Location: Pennsyltucky
Posts: 2,625
i would say the 7AM is an example of extreme overbore and the closer you are to the "red line" i think you called it, small changes will make more noticable differences. i'd like to see the same experiment done with larger diameter bullets to compare the amount of change in V and P to the smaller diameters to see if diameter would have any influence on the percentage of change.
__________________
davesonlinedeals.com
Reply With Quote
  #5  
Old 05-01-2008, 10:03 PM
Platinum Member
 
Join Date: Sep 2004
Location: on the rifle range in Utah
Posts: 2,720
You guys can read something while you're waiting for the new article. Pick up a copy of Sierra's latest reloading manual and flip to the section about the 223 tests in differing twists. They found very insignificant results in running tight twists vs. slow twists as far as velocities were concerned.
__________________
Find it
Range it
Click it
Pull it
Dump it

If it's not far, it's boring.
Reply With Quote
  #6  
Old 05-01-2008, 11:23 PM
Platinum Member
 
Join Date: Feb 2005
Location: USA
Posts: 2,598
gg, many will not let facts stand in the way of preconceived beliefs. Your signature is spot on...
__________________
range it,check the wind, dial in correction, aim and only one shot
Reply With Quote
  #7  
Old 05-02-2008, 01:00 AM
Platinum Member
 
Join Date: Aug 2003
Location: NC, oceanfront
Posts: 3,364
Thanks for sharing the info
You know, every little bit helps
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Similar Threads for: Fast Twist VS Slow Twist
Thread Thread Starter Forum Replies Last Post
Is my twist to fast for a 6/284 stifle Rifles, Bullets, Barrels & Ballistics 8 04-13-2011 08:15 PM
fast twist 250? backyardsniper Varmint Hunting 6 03-23-2011 10:18 PM
7mm Remington mag with a slow twist 30-06 Rifles, Bullets, Barrels & Ballistics 3 03-05-2011 05:03 PM
Fast twist 223 goose316 Guns For Sale 4 08-02-2009 09:47 AM
Fast twist .223 N_dawson Long Range Hunting & Shooting 6 07-19-2009 05:54 AM


All times are GMT -5. The time now is 07:06 PM.


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