How to Mark a Target Bullet Group?

Thomasss

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I have seen it done several different ways and was wondering if there are any one or more ways to properly mark a bullet group on a target?
I have seen some people mark the target by outside edge of the farthest bullets from the group then sub-track one caliber diameter bullet that was shot.
I've also seen people measure the bullet's center's hole of the two farthest bullets.
The edge? The grey mark of the bullet left on paper or the actual hole cut edge made by the bullet?
OR?
 
I've also seen people measure the bullet's center's hole of the two farthest bullets
I measure group size by measuring center-to-center.

There are apps you can use to automate this process by taking picture of your groups.
 
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I have seen some people mark the target by outside edge of the farthest bullets from the group then sub-track one caliber diameter bullet that was shot.

If I’m using calipers that’s how I do it. It’s easier for me to find the edge of the hole than the center.
 
I measure outside edge of hole to outside edge of hole - then subtract one hole diameter. Not bullet diameter, because bullets are typically notably larger than the hole they leave behind.
 
Not bullet diameter, because bullets are typically notably larger than the hole they leave behind.
Yup. Subtracting bullet diameter will usually make the group measurement smaller than it should be.

I have a target here that was shot with a 9mm.

Eyeballing the centers of the two farthest apart rounds gives a measurement of 1.57"

Measuring from outside edge to outside edge and subtracting hole diameter gives 1.571"

Measuring from outside edge to outside edge of the two farthest and subtracting nominal bullet diameter gives a measurement of 1.41" which is obviously significantly too small. That's because the average hole diameter is significantly smaller than the nominal 9mm bullet diameter of 0.355".
I have seen it done several different ways and was wondering if there are any one or more ways to properly mark a bullet group on a target?
Typically group sizes are quoted as center-to-center (ctc) size of the two rounds in the group that are farthest apart. There are a couple of ways to obtain accurate ctc measurements but the method doesn't matter as long as the result is correct.
 
If the target was shot beyond "one ragged hole" range, I measure like IK, outside to inside of the wide hits.
If I get "one ragged hole" the range was probably too short to brag about.
 
There are instruments available, or you can make one yourself, for precisely measuring groups center to center. I use one like the one shown here with George Kelbly Jr measuring benchrest targets at the SuperShoot. He measures and records hundreds of targets per day during the tournament and can measure and record a target in about 30-seconds. Supershoot.JPG
 
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Now days I'm simple , I keep a penny dime nickle quarter and fifty cent piece in MY pocket ,depending on distance I use one to cover the group or I don't . I'm NO longer BR or competitively shooting either .

Winchester white box upper left quadrant #5 ,POA same ,one fouler #15 hand loads at 200 yd. on the dirt with a stock Bushmaster ES2XM15 20" Target AR15 . Circa 1997-98 . Witnessed by several local PD assembled on our Range . I'll never forget when so many said chrome bore ,No good won't shoot accurately . Yep everybody's a critic as well as an expert .
 

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