Ordnance Notes, No. V. 1873; 45 Colt, 50 yards

[Savvy Jack]

Washington, June 27th 1873

Shooting the 45 Colt out to 50 yards.

10 Shots, absolute deviation, 3.11" Group

[Larry Gibson]

The "deviation" method of measuring groups back then was different than what we use these days. That 3.11" would be the average distance from a determined center of the group of all 10 shots. I.E. determine the center of the group then measure the distance from there to all ten shots. Add up those distances then divide by 10 for the "average deviation".

That 3.11" back then would be a 9 - 10" group as we measure groups today.

[Savvy Jack]

The "deviation" method of measuring groups back then was different than what we use these days. That 3.11" would be the average distance from a determined center of the group of all 10 shots. I.E. determine the center of the group then measure the distance from there to all ten shots. Add up those distances then divide by 10 for the "average deviation".

That 3.11" back then would be a 9 - 10" group as we measure groups today.

Larry, you ruined it...LOL

[mjwcaster]

Thanks for posting that Larry.

I noticed the ‘absolute deviation’ right away, but wasn’t entirely sure about it.
I’ve only seen it as ‘mean’ deviation, mostly from Molan on ar15.com.

A quick search shows-
absolute mean deviation
standard deviation
absolute median deviation

I like crunching numbers but it’s been many years since school and statistics was never a strong suit.

Just now researching the difference between mean, median and standard is causing my eyes to glaze over.

But I do appreciate how deviation can provide better numbers for the military vs extreme group spread and always enjoy having more data, even if I don’t understand all of it.

[Savvy Jack]

Thanks for posting that Larry.

I noticed the ‘absolute deviation’ right away, but wasn’t entirely sure about it.
I’ve only seen it as ‘mean’ deviation, mostly from Molan on ar15.com.

A quick search shows-
absolute mean deviation
standard deviation
absolute median deviation

I like crunching numbers but it’s been many years since school and statistics was never a strong suit.

Just now researching the difference between mean, median and standard is causing my eyes to glaze over.

But I do appreciate how deviation can provide better numbers for the military vs extreme group spread and always enjoy having more data, even if I don’t understand all of it.

My head has been hurting for days....I needed help :-)

290614

[30calflash]

Looks like a lot of older methods of measurements have gone by the wayside and now leave us wondering exactly what they actually did do with the numbers they posted.

I know string measure has been used a long time, even still in some shooting circles.

[44MAG#1]

The "deviation" method of measuring groups back then was different than what we use these days. That 3.11" would be the average distance from a determined center of the group of all 10 shots. I.E. determine the center of the group then measure the distance from there to all ten shots. Add up those distances then divide by 10 for the "average deviation".

That 3.11" back then would be a 9 - 10" group as we measure groups today.

I knew that. It is actually simple to do but takes time and figuring, or ciphering according to Jethro Bodine. I have even listed ES and SD

[AndyC]

The "deviation" method of measuring groups back then was different than what we use these days. That 3.11" would be the average distance from a determined center of the group of all 10 shots. I.E. determine the center of the group then measure the distance from there to all ten shots. Add up those distances then divide by 10 for the "average deviation".

That 3.11" back then would be a 9 - 10" group as we measure groups today.

Welp, I for one learned something today... I had no idea.

[bedbugbilly]

Interesting thread . . . .

Thanks Larry . . . . . . interesting info on how they did it.

[44MAG#1]

I shot a 10 shot group a while back and did the math. The ES was 4.75 inches. Ave accuracy was 1.425 inches, SD was .77077934 inches population and .81247329 inches sample. Took a while for a simpleton like me to do the math but I did it. The 1.425 inch accuracy looks a lot better that the 4.75 inch group size.

[Savvy Jack]

I shot a 10 shot group a while back and did the math. The ES was 4.75 inches. Ave accuracy was 1.425 inches, SD was .77077934 inches population and .81247329 inches sample. Took a while for a simpleton like me to do the math but I did it. The 1.425 inch accuracy looks a lot better that the 4.75 inch group size.

Kinda sounds like Common Core to me...LOL

[Outpost75]

Then some old references use Figure of Merit or Mean Diagonal.

IIRC FOM is the average of max. horizontal and max vertical dispersion.
Less sure of Mean Diagonal, but that sounds alot like average extreme spread for a sample of several groups. Would be nice to find an historical reference for that.

[44MAG#1]

Then some old references use Figure of Merit or Mean Diagonal.

IIRC FOM is the average of max. horizontal and max vertical dispersion.
Less sure of Mean Diagonal, but that sounds alot like average extreme spread for a sample of several groups. Would be nice to find an historical reference for that.

Go to link. http://ballistipedia.com/images/9/9a/Is_Group_Size_the_Best_Measure_of_Accuracy_by_J.E. _Leslie_III.pdf read down to Figure of Merit etc.

[ddixie884]

Cool....................

[Jtarm]

Go to link. http://ballistipedia.com/images/9/9a/Is_Group_Size_the_Best_Measure_of_Accuracy_by_J.E. _Leslie_III.pdf read down to Figure of Merit etc.

https://media0.giphy.com/media/tZ6zAdNZbWOhq/giphy.gif

Think I’ll stick with group size.