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Standard Deviation
konamtbiker
Member Posts: 284 ✭✭✭
To my understanding the lower standard deviation you can get out of your ammo the better. Today at school an instructor said that standard deviation does not help out on accuracy? Want some other opinions on the matter. Thanks
Comments
Tim
I think this instructor needs to make a popping noise. SD = average constant velocity. The farther out you shoot the more it matters. It's a simple matter of physics, slow bullets drop faster than fast bullets. Like perry said though, the average still has to correlate to the sweet spot of the firearm. Having bad harmonics by running the bullet 100 fps too slow will send the extreme spread all over the place. They correlate to one another but each has to match it's intended target range.
If this is regarding how much time you spend prepping brass and carefully working up loads to get everything to shoot just right, then you need to decide what your accuracy needs are. A lot of 100-200 yd. bench shooters don't weigh loads. They have a good measure and can throw loads that are within 1-2 tenths of a grain. That little difference isn't going to make a difference with accuracy at those short distances. Not nearly as much as having a load that doesn't harmonically match the barrel. Long range shooters can't afford to have bullets dropping out of the circle though. and loss of velocity by 50-100 fps will make a big difference.
Standard Deviation is one small part of the whole picture. It helps tell you how consistent your ammunition is. But even this can be suspect depending on the conditions under which the data is collected. Inexpensive chronographs might not be ideal for collecting this piece of information. Sunlight or lack thereof, poor screen quality and dozens of other variable can have an impact on just this one number, so it can be suspect.
The reason that this number is not a strong indicator is because there are other variables that can have a greater impact on accuracy. One of the biggest for long range shooting is the wind. When shooting at 600 through 1,000 yards, the wind can switch more than once at different distances. Put yourself at the bench and think about all of the things that can change your accuracy when shooting at targets. Standard Deviation is just a part of the picture. It deserves consideration but it isn't the end all.
How's school going?
Best.
http://www.shootingsoftware.com/ftp/Perverse Nature of SD.pdf