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
The do all 6.5 bullet????
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: 864510" data-attributes="member: 28191"><p>No.</p><p></p><p>If the Miller twist rule predicts a Sg below 1.2 for a monometal or a jacketed lead bullet, the results are not going to be good unless an error was made measuring the twist rate, bullet length, or atmospheric conditions. We've confirmed the Sg predicted by the Miller twist rule is within 5% for a number of different bullets. We've also confirmed (repeatedly) the results reported by Sierra and Litz that you get some weird BC effects below Sg = 1.25. For Sg between 1.0 and 1.25, you will usually not see tumbling, and you may see decent accuracy, but you will see large shot to shot variations in BC as well as reduced BC, neither of which is conducive to long range accuracy. See: <a href="http://arxiv.org/ftp/arxiv/papers/1309/1309.5039.pdf" target="_blank">http://arxiv.org/ftp/arxiv/papers/1309/1309.5039.pdf</a></p><p></p><p>The 140 VLD works well enough at 980 ft and 40 deg F because the Miller Twist Rule predicts Sg of 1.22. From the bullet construction, I'd estimate the Twist Rule is a tad low for this bullet (due to the open tip), so I'd say the actual Sg is closer to 1.27. This is an acceptable Sg for precision use, but you might hit trouble at sea level on a cold, dry day. The bullet would not tumble from a high quality barrel with a 1 in 9" twist, but it would suffer from reduced BC and possibly large shot to shot variations in BC.</p><p></p><p>Various recommendations for Sg > 1.4 or Sg > 1.5 are based on uncertainties in bullet dimensions and atmospheric conditions. If you get these details right, you can be confident in the twist rule predictions within the considerations above, and only expect trouble of the predicted Sg is below 1.25 or 1.3.</p></blockquote><p></p>
[QUOTE="Michael Courtney, post: 864510, member: 28191"] No. If the Miller twist rule predicts a Sg below 1.2 for a monometal or a jacketed lead bullet, the results are not going to be good unless an error was made measuring the twist rate, bullet length, or atmospheric conditions. We've confirmed the Sg predicted by the Miller twist rule is within 5% for a number of different bullets. We've also confirmed (repeatedly) the results reported by Sierra and Litz that you get some weird BC effects below Sg = 1.25. For Sg between 1.0 and 1.25, you will usually not see tumbling, and you may see decent accuracy, but you will see large shot to shot variations in BC as well as reduced BC, neither of which is conducive to long range accuracy. See: [url]http://arxiv.org/ftp/arxiv/papers/1309/1309.5039.pdf[/url] The 140 VLD works well enough at 980 ft and 40 deg F because the Miller Twist Rule predicts Sg of 1.22. From the bullet construction, I'd estimate the Twist Rule is a tad low for this bullet (due to the open tip), so I'd say the actual Sg is closer to 1.27. This is an acceptable Sg for precision use, but you might hit trouble at sea level on a cold, dry day. The bullet would not tumble from a high quality barrel with a 1 in 9" twist, but it would suffer from reduced BC and possibly large shot to shot variations in BC. Various recommendations for Sg > 1.4 or Sg > 1.5 are based on uncertainties in bullet dimensions and atmospheric conditions. If you get these details right, you can be confident in the twist rule predictions within the considerations above, and only expect trouble of the predicted Sg is below 1.25 or 1.3. [/QUOTE]
Insert quotes…
Verification
Post reply
Forums
Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
The do all 6.5 bullet????
Top