Forums
New posts
Search forums
What's new
Articles
Latest reviews
Author list
Classifieds
Log in
Register
What's new
Search
Search
Search titles and first posts only
Search titles only
By:
New posts
Search forums
Menu
Log in
Register
Install the app
Install
Forums
Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Long bullets require fast twist barrels?
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Message
<blockquote data-quote="Michael Courtney" data-source="post: 864783" data-attributes="member: 28191"><p>From Litz 2009 p. 160 (Emphasis in the original):</p><p></p><p>It's common knowledge that bullets fired with adequate gyroscopic stability can become unstable at long range, tumble, and keyhole in the target. Most shooters assume that the problem is a lack of gyroscopic stability, and sometimes try to remedy it by using a faster twist barrel. A faster twist barrel certainly does increase the gyroscopic stability of the bullet both at the muzzle and downrange. However, <strong><em>when a bullet tumbles at <u>long</u> range, it's not because of a lack of <u>gyroscopic</u> stability, but through a lack of <u>dynamic</u> stability.</em></strong></p><p></p><p>At Litz goes on to explain, this effect most commonly is seen somewhere around the sonic transition, but there are cases where lack of dynamic stability causes tumbling at long range even though the bullet is nowhere near the sonic transition. The dynamic stability condition is complex (see: <a href="http://www.nennstiel-ruprecht.de/bullfly/dynacond.htm" target="_blank">http://www.nennstiel-ruprecht.de/bullfly/dynacond.htm</a> ). Even though it may not immediately be clear in this case why the bullet becomes dynamically unstable, it is clear that the dynamic stability rather than the gyroscopic stability is the problem. A faster twist barrel may not fix the problem. All of the terms in the dynamic stability equation are characteristics of the bullet itself. Increasing the gyroscopic stability (with faster twist) is hopeless if the dynamic stability becomes equal to one and the dynamic stability condition becomes impossible to fulfill. </p><p></p><p>If the bullet has dynamic stability problems, faster twist rates, higher elevations, and higher muzzle velocity can (at best) push the onset of dynamic instability out to longer ranges. But if the problem is already appearing at 600 yards, I would be surprised if the bullet can ever be made to shoot reliably at 1500 yards.</p></blockquote><p></p>
[QUOTE="Michael Courtney, post: 864783, member: 28191"] From Litz 2009 p. 160 (Emphasis in the original): It's common knowledge that bullets fired with adequate gyroscopic stability can become unstable at long range, tumble, and keyhole in the target. Most shooters assume that the problem is a lack of gyroscopic stability, and sometimes try to remedy it by using a faster twist barrel. A faster twist barrel certainly does increase the gyroscopic stability of the bullet both at the muzzle and downrange. However, [B][I]when a bullet tumbles at [U]long[/U] range, it's not because of a lack of [U]gyroscopic[/U] stability, but through a lack of [U]dynamic[/U] stability.[/I][/B] At Litz goes on to explain, this effect most commonly is seen somewhere around the sonic transition, but there are cases where lack of dynamic stability causes tumbling at long range even though the bullet is nowhere near the sonic transition. The dynamic stability condition is complex (see: [url]http://www.nennstiel-ruprecht.de/bullfly/dynacond.htm[/url] ). Even though it may not immediately be clear in this case why the bullet becomes dynamically unstable, it is clear that the dynamic stability rather than the gyroscopic stability is the problem. A faster twist barrel may not fix the problem. All of the terms in the dynamic stability equation are characteristics of the bullet itself. Increasing the gyroscopic stability (with faster twist) is hopeless if the dynamic stability becomes equal to one and the dynamic stability condition becomes impossible to fulfill. If the bullet has dynamic stability problems, faster twist rates, higher elevations, and higher muzzle velocity can (at best) push the onset of dynamic instability out to longer ranges. But if the problem is already appearing at 600 yards, I would be surprised if the bullet can ever be made to shoot reliably at 1500 yards. [/QUOTE]
Insert quotes…
Verification
Post reply
Forums
Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Long bullets require fast twist barrels?
Top