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
Reloading
Es/sd
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="dsculley" data-source="post: 1145187" data-attributes="member: 77514"><p>ES - Extreme spread - the difference between your fastest and slowest shot in a string. While helpful, this is not nearly as good a tool as SD (Standard Deviation).</p><p></p><p>SD - Standard Deviation - a predictor of the range of velocities of all your shots based on a sample. (This is the most important of the two numbers)</p><p></p><p>Example: Assumptions for this example: ES = 9, SD = 2.5, Avg Velocitiy = 3000 fps</p><p></p><p>The ES tells you that on this batch of ammo, you did a good job and total variation in THIS string was low.</p><p></p><p>Using SD for this string as 2.5 and assuming a normal distribution for your ammo, you can expect that 68.2% of your rounds will fall within 2 standard deviations (+1 & -1), 95.4% of your rounds will fall within 4 standard deviations (+2 & -2), 99.6% of your rounds will fall within 6 standard deviations & 99.8% will fall within 8 standard deviations.</p><p>3000 fps avg</p><p>68.2% will be between 2997.5 & 3002.5 (ES = 5)</p><p>95.4% will be between 2995 & 3005 (ES = 10)</p><p>99.6% will be between 2992.5 & 3007.5 (ES = 15)</p><p>99.8% will be between 2990 & 3010 (ES = 20) </p><p></p><p>As you can see, the expected extreme spread (> 20 fps) of your total population is more than twice ES of your string. Using SD, you can use ballistics programs to see how this will affect your point of impact in determining if this load is acceptable for your purposes. </p><p></p><p>I think any shooter on this forum would love to have an ES of 9 and SD of 2.5, but many shooters don't really know how to interpret the figures, especially SD. As hand loaders, our goal is for consistency in our processes so that we will have consistency in our results.</p><p></p><p>I hope this helps.</p><p></p><p>Dennis</p></blockquote><p></p>
[QUOTE="dsculley, post: 1145187, member: 77514"] ES - Extreme spread - the difference between your fastest and slowest shot in a string. While helpful, this is not nearly as good a tool as SD (Standard Deviation). SD - Standard Deviation - a predictor of the range of velocities of all your shots based on a sample. (This is the most important of the two numbers) Example: Assumptions for this example: ES = 9, SD = 2.5, Avg Velocitiy = 3000 fps The ES tells you that on this batch of ammo, you did a good job and total variation in THIS string was low. Using SD for this string as 2.5 and assuming a normal distribution for your ammo, you can expect that 68.2% of your rounds will fall within 2 standard deviations (+1 & -1), 95.4% of your rounds will fall within 4 standard deviations (+2 & -2), 99.6% of your rounds will fall within 6 standard deviations & 99.8% will fall within 8 standard deviations. 3000 fps avg 68.2% will be between 2997.5 & 3002.5 (ES = 5) 95.4% will be between 2995 & 3005 (ES = 10) 99.6% will be between 2992.5 & 3007.5 (ES = 15) 99.8% will be between 2990 & 3010 (ES = 20) As you can see, the expected extreme spread (> 20 fps) of your total population is more than twice ES of your string. Using SD, you can use ballistics programs to see how this will affect your point of impact in determining if this load is acceptable for your purposes. I think any shooter on this forum would love to have an ES of 9 and SD of 2.5, but many shooters don't really know how to interpret the figures, especially SD. As hand loaders, our goal is for consistency in our processes so that we will have consistency in our results. I hope this helps. Dennis [/QUOTE]
Insert quotes…
Verification
Post reply
Forums
Rifles, Reloading, Optics, Equipment
Reloading
Es/sd
Top