Originally Posted by dk17hmr
I am still learning all the small details of LR hunting and shooting. I have been shooting long range for a while but obviously didnt know anything until I started reading on this site. ES? SD?
I am using 64gr of H4831SC with Remingotn 9 1/2 primers in RP cases, seated just off that lands. I have an 8 pounder of this powder that is when I am using it. I might have to give other powders a try for more speed, but I am be getting a 300 RUM next week in trade so I might just use that for speed. Because the load I am flinging out of the WSM right now goes into tight groups.
Sounds like a good reason to me. Speed isn't necessary unless you want to kill something big way out there. ES and SD are numbers used to verify if you have a good load shooting consistently. ES= Extreme Spread- The speed between your fastest and lowest shot tested. 2600 as a low and 2635 as a high means you have and Extreme Spread or ES of 35fps. This number if it is to big of a difference would need to be tightened up in order to shoot accurately past 300 to 400 yards. At extreme range a slow round could mean a low shot or a fast round could mean a high and a miss with either or wounding. You won't see the spread at short range unless you are in the 50 to 100 fps range of variance.
SD or Standard Deviation is the measurement of the average between a shot based off of the average known velocity. If your average speed for 5 shots fired equals 2635fps, then you take that number and subtract it from each shot fired known actual velocity. Just for practical purposes:
1. 2630- (avg.)2635= 5fps
2. 2620- 2635=15fps
Total 34/5(total shots fired in string)=6.8fps
Now these number obviously are random and they are based off of your velocity given in your post. So your Standard Deviation or SD is 6.8fps from shot to shot on average. In this example your High is 2640 and your Low is 2620 with an extreme spread or ES of 20fps. Hope this helps. The smaller your SD and ES are, the more likely you are able to hit stuff at extreme range. My number equate to ES=11fps and SD=3fps. Those are the numbers you want to achieve. If you can get them smaller, that is what you really want. This can be done by playing with powders, primers, and charge weights. The more in the case doesn't always equal tighter numbers. Hope this helps! Keep shooting and let us know how the RUM works out.
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