Measuring Groups

S

SGJennings

New member
I'm a newbie. I'd like to have some method of recording my group sizes, but I don't know beans about measuring them accurately.

Can someone point me to anything helpful? Articles, tools, anything.

Also, I saw for sale somewhere a tool that estimated groups based on the outside edges. Can't google it up or find it through searches here. Can anyone point me to it?
 
The easy way is to measure to the outside edges of the two widest shots in the group then subtract the bullet diameter.

Unfortunately the hole in the target is a bit smaller than the diameter of the bullet and depends on the paper the target is printed on. SO, measure a single bullet hole accurately with a dial or digital caliper, then subtract that measurement from the measurement of the two widest shots in the group. That will give you the center to center measurement of the to widest bullet holes. That's plenty close enough for non-competition use.

For competition there are devices that clamp onto a caliper that have circles scribed on them for various size bullet holes. They're the best way, but a more expensive.
 
To what degree of accuracy? You can do it to within a few hundredths by getting a precise outside to outside length on the furthermore bullet holes and then subtracting bullet diameter. That method is inaccurate mostly because bullets mostly don't leave exactly caliber sized holes; the holes are sometimes smaller but mostly larger than the bullets. The level of inaccuracy (+/- .03-.05 or so) in this method would be huge in a BR competition but won't matter if you are just keeping personal track of load development.

If you have to get it right, you have to buy a recticle purpose made to put on a caliper. I'll take a picture of one and attach when I have a chance.

Edit, Larry and I seem to have made identical replies at the same time. We'll have to refer this matter to the Department of Redundancies Department---

Edit (squared): here's the picture, just FYI. There are 3 circles on the reticle, one for 22, 6mm and 30 cal. You center the appropriate circle on a far hole, push the button to freeze the device to the target paper and then move the movable part with the reticle attached to be centered on the opposite far hole and direct read the result.

If you have a scanner, you can scan the image and use the program "On Target" to perform the calculations.

measuring.jpg
 
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Since it's just for load development, sounds like the "measure outside and subtrace one measure bullet hole" method would be great.

Thank you, guys, I appreciate it very much.

My son and I are having a blast with this. Well, we're having a blast when I can tear him away from his, admittedly, smokin'-hot girlfriend.
 
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SGJennings said:
Since it's just for load development, sounds like the "measure outside and subtrace one measure bullet hole" method would be great.

Thank you, guys, I appreciate it very much.

My son and I are having a blast with this. Well, we're having a blast when I can tear him away from his, admittedly, smokin'-hot girlfriend.
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Hey, IF the girlfriend is the real deal and IF they go on to marry and settle in...... you'll regain a best shooting buddy! And a friend for your wife too.....for life.

I agree, use the calipers, subtract a (measured) bullet hole. OR, just subtract .243 or .224 or whatever every time. The resultant measurement will be too small but for comparison w/you and the boy..... no harm.

Good Stuff.

al
 
If the holes farthest apart are clear and distinct, just measure from the inside of one to the outside of the other.

If the holes are just one ragged mess, of course, you cannot do that. Then you measure outside to outside and subtract bullet diameter.
 
Montana Pete said:
If the holes farthest apart are clear and distinct, just measure from the inside of one to the outside of the other.

If the holes are just one ragged mess, of course, you cannot do that. Then you measure outside to outside and subtract bullet diameter.
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JEEpers!! If there's separate holes you can measure with a YARDSTICK fer cryin' out loud! That ain't a "group"....... that's a shotgun blast!

al
 
I have a clear plastic circle template that i got from a office supply store that i use at the range for informal meausurements. It was cheap, only about the size of a sheet of paper, and lets me leave the calipers at home. Has served me well. Good Shooting Lightman
 
Sorry I can't resist....

...and whatever you do, don't forget to measure your all time smallest 3 shot group (or three of the five shots) and then get on here and post that your rifle shoots that size "all day long"!:D

OMG....I am starting to channel Bill Ohio...someone get me a priest.:p
 
Shoot a "measuring shot" anywhere out of the group. Use digital calipers to measure your "measuring hole" -then click the "zero" button. Now measure outside to outside of your group and your group size is calculated for you, just read the caliper. joe :)
 
Just my humble opinion but, the only place that precise measurements are necessary are at a Match and there are guys that do it for you, officially and with the right equipment. It's a waste of time to agonize over the exact size hole a bullet makes and trying to determine if that group is a .219" or a .226". What difference does it make?

Most guys I know, when practicing or developing a load, simply measure outside to ouside with a caliper, and subtract one bullet diameter. Hell, most of the time we don't even do that. After years of shooting you only need to look at a group and you can tell very nearly it's size. And you sure as hell can tell a bad group when you see one and you don't even bother measuring them.:rolleyes:

Ray
 
Cheechako said:
Just my humble opinion but, the only place that precise measurements are necessary are at a Match and there are guys that do it for you, officially and with the right equipment. It's a waste of time to agonize over the exact size hole a bullet makes and trying to determine if that group is a .219" or a .226". What difference does it make?

Most guys I know, when practicing or developing a load, simply measure outside to ouside with a caliper, and subtract one bullet diameter. Hell, most of the time we don't even do that. After years of shooting you only need to look at a group and you can tell very nearly it's size. And you sure as hell can tell a bad group when you see one and you don't even bother measuring them.:rolleyes:

Ray
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Ray. That is a very good point.
It only matters at a match. With real competition and a time limit. :eek:
If hunting. A prairie dog or ground hog doesn't care if it was a .219" or a .226". :)
 
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I agree with Dusty

This Forum is about sharing.

If your Son has, Quote, a "smoking hot girlfriend", he should be willing to at least share some photos.

In return, I will be glad to post some photos of my new little Dachund Hound, Maddie...........jackie
 
Jackie your right. This site is about sharing.
I have learned a lot here. I started reloading and shooting in the dark ages. Before the Internet.
My gun shop only had 1 book. The library wanted nothing to do with shooting.:eek: Lady said do I have to call the police. Then started mumbling.
The ranges were an hour drive. The desert was closer. :)

By the way, Jackie got any primers ya want to get rid of. I know this guy. He is newer than me to Benchrest......Just joking. Texas is to far too drive, anyway.
 
JEEpers!! If there's separate holes you can measure with a YARDSTICK fer cryin' out loud! That ain't a "group"....... that's a shotgun blast!
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This makes no sense to me at all.

What's with the yardstick?

What the heck are you even talking about?
 
zippy06 said:
"On Target" is a great program. And free. :)
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I would agree with Zippy. The program is easy to use and fairly accurate for non formal shooting and load development. I use it all the time. The best part is that it is free.

Danny Kibler
 
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