Measuring groups?

[wisconsinteacher]

How do you guys measure your groups? I did some shooting today and want to make sure I measure my groups right so I can post some results.

 

[DrMike]

Measure the distance to the outer edge of the widest point in the group. Subtract the calibre. That is groups size.

 

[JD338]

The measurement is taken at the widest point between shots, center to center. The easiest way is to measure the furthest edges of the bullet holes and subtract the bullet diameter. Example widest points measured is 1.000" - .338" = .662".

JD338

 

[wisconsinteacher]

So out of a 3 shot triangle, you only measure the two furthest shots. I thought you measured each one (for 3 shots, 3 measurements A-B/A-C/B-C) then divided the number.

 

[JD338]

Measure the widest point.

JD338

 

[DrMike]

WT,

DON gives an example of measuring a group at this thread: http://www.noslerreloading.com/phpBB2/viewtopic.php?f=4&t=15066&start=15. Sometimes, actually seeing what is done can be helpful.

 

[onesonek]

Here's another pic for example.
Group measures .490 on the outside, minus the bullet dia. equals group size center to center as Mike and JD stated

 

[romex2121]

dang !!! :shock: if your groups look like that i dont think id worry about it to much :lol:

 

[aka Hunter]

The above suggestions of measuring the distance to the outer edge of the widest point in the group then subtracting the calibre size is great in theory, but it may leave something to be desired in application. If you're not using wadcutters, oftentimes (always (?)) the bullet doesn't leave a full-diameter hole in the paper; thus, the measurement to the widest point likely will be "short" (unless, maybe, you're using some sort of reticle used for scoring benchrest targets); thus, when you subtract the caliber size from that measurment the result is a smaller number than the actual size of the group. Granted, the error won't be a bunch, but be aware that it's likely wrong.

 

[onesonek]

That is true to a point, but it is indeed small. The way I was shown/taught, is to not measure the hole, but the imprint surrounding the hole made by the bullet. Which if you look closely at the pic, you will see a black ring made by the bullet. If you just made a single shot, and then measured that ring, it will be pretty close,,,,at least I have found it so. It will vary somewhat depending on target paper used also. But we are not scoring anything official here, so in reality, measuring to the nearest .01" would satisfy most curiosities.

 

[SJB358]

Heck, I round up to the nearest 1/2"! No need to get too picky! I need to round up, just to keep up with Jim and Joel's groups. Scotty

 

[onesonek]

ya but :lol:

 

[backcountryhunter]

IF you're not trying to measure for a competition or somethin' like that there it is just as easy to measure from the outside of one hole to the inside edge of the farthest hole and THAT will give you a pretty good assessessment of the "group"