Graybeard Outdoors banner

For precision and accuracy determinations

1576 Views 14 Replies 8 Participants Last post by  Paladin
Determining Minutes of Angle(M) subtended on target:
M=60[ Tan -1 (group size in inches/range in inches)]
where M= number of minutes of angle subtended or 1 min = 1/60 degrees = 1.047 inches at 100 yards

Minutes of angle subtended by a target group at 100 yds.
M = Target group size (inches)/ 1.047

Determining Standard Deviation (target precision or velocity)
s.d. = square root of sigma(dn)2(squared)/N-1
where s.d. = standard deviation(precision = inches, velocity = feet per second)
dn = vertical distance from reference line in inches(precision) or velocity deviation of individual round from average velocity in feet per second (velocity)
N = number of rounds in group

These are a few formulas I use to determine MOA, velocity, and precision of individual handloads. These take a good bit of human error out of measuring groups with a ruler and/or micrometer. There is a complete chapter dedicated to using these formulas in Precision Handloading by John Withers. :eek: :-D
1 - 15 of 15 Posts
Precision and Accuracy

Oh, I understand it now. Thanks Nimrod
Precision and Accuracy

Makes sense when it's put to you this way.
cool but...

i've got a 2 year college degree, but i think i'll still just use the 'ol dial calipers'. :) :) i hate thinkin. :wink:
HA.... :eek: I'm with KYODE I too have a 2year degree but I'll just use the calipers
You guys stopped too early. I have a four year degree and use a 12" three sided ruler marked in 10s of an inch. You're kidding yourself if you try to measure closer than 1/10". :)

It took me much more than 4 to get credit for 4 but I was having a lot of fun

It took me much more than 4 to get credit for 4,but I was having lots of fun( at least it seemed so at the time ). Thank goodness my 35P calculates SD for me. I did sit down one time and scratch my head long enough to figure 1 MOA was somewhere close to 1" at 100yd. Probably why I don't have any hair left too. I always wondered how everybody measured a group to the nearest .001". GOOD SHOOTIN', Walt :-D

See less See more
Alright already, So I don't have a drinking problem - just a hobby problem. Wait , I don't have any hobbies just obsessions! :)

I can't believe no one caught the "sigma" in those formulas that was not defined. I've used those formulas for ten(10) years and still have to go to the book when I sit down and do my calculations. They actually look harder then they really are.

Graybeard, I sat down last night and put together a .27" group (actually only two shots) using a 7mm bullet. I had three different people measure it and came up w/ three different measurements. I guess my point is the amount of error in measuring holes that close together. Pretty impressive group all the same from a 7-30. (This is where all those formulas came from!)
Kyode - you should know me better than that - I'll post the formulas at Gary's place and see what the guys say!
Precision and Accuracy

To each his own,

When measruing groups at 100 yards some use calipers, GB uses a 3 sided ruler and Nimrod uses his formulas. I have an old red yard stick in the back of my pick-up. Works for me
Finally - someone who understands what is really being said here!! :wink:
i agree

to each his own sounds good. if i'm just messin around i'll just measure with a tape rule for a close estimate. but if i get excited and it looks like a new world record (for KYODE) then i pull out the dial calipers, if i remembered to bring em. :lol:

whats a sigma ! :? :D
Re: i agree

KYODE said:
whats a sigma ! :? :D

I think that's a S&W handgun isn't it? Or is that a stigma? :)

Precision and accracy

You know Nimrod I just don't know what this forum is coming to. Now I always knew there was a bunch of smart asses on this forum but now even GB is getting in on it. Where will it end.
We had some fun Nimrod and you got a lot of replies and for that I really do thank you for your post.
Thank you Oldman, but I probably brought it on myself - as usual. My wife is always reminding me that not everybody takes their hobbies so seriously. I'm not sure which is worse - How serious I get, or how much fun I have doing it. Knowledge is power, and I don't want to leave this world a weakling.

P.S. Did ya know the Crappies bite the best In Lake Redman/Pa. when the water temp. Is 55-57 degrees not 54-58 (here we go again).
rulers? we don't need no stinking rulers, just shoot one hole, than you just need to know what caliber your shooting.
1 - 15 of 15 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.