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How do you measure groups?

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I thought most people used the old "distance between two knuckles of your finger is about an inch" method.

Personally, some days it's more effective to revert back to the Biblical measurement of cubits...or even barn walls. I need to practice more.
 
The acceptable way to measure groups for the internet is to throw a quarter onto the target and take a picture of it. Never under any circumstances mention the range the target was shot.
Click to expand...

:D:D And make sure all flyers are off camera.
 
The Brits do extreme spreads only.

I learned this checking Eley's web site on their .22 rimfire Tenex match ammo. Group sizes at 50 yards were almost a quarter inch larger than what folks in the USA get testing their match rifles. So I emailed the USA rep and he replied that they don't subtract bullet diameters from the numbers they get. They do the same for centerfire rifle and pistol ammo, too.
 
Like Warp,
"I'm good with measuring the farthest holes, far edge to near edge,"

This assuming I am not shooting so close or such a fine rifle that I get "one ragged hole."

Also shoot at a regulation target and take the score. Or make up an overlay so you can score a group not centered at that range.
 
With a vernier.

If the group is not a one hole then from the outside of the one furtherest hole to the inside of the other furtherest hole then you dont have to subtract one calibre. If one hole then outside to outside less one calibre.

I always include so called flyers as in my opinion flyers are operator error. In any event in a competition you cannot exclude "flyers" from your score so they do count.

I see many shooters BS themselves and will discount poor shots from the group. Also for me accepting flyers means accepting that the ammo is bad and that you need not address the issue as a shooter.

I was on the range once with a mate who was shooting 30-06 with cheap factory ammo. He could not get a group under 1.5" and was getting the odd flyer. There was a youngster on the range who happened to be a National Junior Shooting Champion. My friend in desperation asked him to shoot a group just to see if it was the ammo (he was convinced it was). The kid shot a perfect cloverleaf first off, big lesson learnt right there.
 
I once saw a gunzine writer in action. He laid out his target for the gun he was plugging, er, testing to be photographed. It was artfully arranged with a close, well centered group framed with the gun barrel and ammo box. Just coincidence the props covered the wide shots, I am sure.
 
The acceptable way to measure groups for the internet is to throw a quarter onto the target and take a picture of it. Never under any circumstances mention the range the target was shot.
Click to expand...

Absolutely! :D That has to be one of my biggest pet peeves, but it takes second place to people simply saying their run shoots 1 MOA!

I shoot 10-round groups; as many as I can afford to shoot on any given range trip. I measure the distance from the outside edges of the bullets that are furthest apart, then I subtract the bullet diameter. I average out the multiple groups and then I report.

Why 10 shots? Molon's write-up best explains it: http://www.ar15.com/forums/t_3_118/279218_.html

The internet is full of people whose rifles magically shoot 1 MOA all day long with military surplus ammo. They love to argue with the numbers of 10-shot groups and they have no hesitation of telling you that "you ain't no rifleman" when all they've ever done is cherry-picked a few 3-shot groups and dismissed errant rounds as "flyers."
 
I'm a simple man so I do things simply. I use a set of calipers to measure to the furthest point of the outside edges of the holes and minus 1 full caliber value.

Example: Shooting the 30-06 you get a number of .622", minus .308" leaves a group of .314" on center.
 
Some years ago, I called Lake City Army Ammo Plant about an accuracy issue with some 7.62 NATO match ammo our team was issued. After resolving the issue, the ballistics engineer I talked with told me the following.....

A new hire was helping him test a lot of match ammo shooting many dozens of shots on their 600 yard test range. They got the target with a couple hundred holes in it with an extreme spread of about 8 inches. That young ballistics enginner mentioned to the old timer: "Wow, look at all those half-inch 5-shot groups on that target." To which he replied: "Yes, 5-shot groups that tiny at 600 yards are very impressive." Then the youngster replied: "Yes, that's right. Too bad they're not all at the same place in that 8 inch cluster." The senior engineer's final comment in so many words: "You'll be good to have around testing ammo for accuracy. You understand better than most folks what ammo accuracy is all about, what proper testing will show and how to interpret the results."

Fliers? There ain't no such thing as fliers. Every shot fired goes exactly where the ammo, rifle and shooter positioned the muzzle axis to put that bullet in flight as it left the barrel. Where that axis points is determined by the quality and repeatability of those three parts of the shooting system.
 
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Depending on the day and the gun, I sometimes have to use a yardstick or surveyors equipment. I usually round to the nearest foot. :)
 
If it is your intent to measure (I've measured fewer than a dozen in 30+ years), mount the target to a firm backer that is clean behind your POI. Cardboard is too soft, corrugated plastic or plywood work well.

I measure outside edge to outside edge and subtract caliber while keeping target flattened out on the bench (backer removed). More accuracy than that means more work for me and my targets cannot compete with BR shooters' numbers anyway. 10-rounds is my number as well, usually at 100 yds. for rifle, 50 yds. for rimfire and 25 yds. for pistol.

I suppose with multiple targets you could buy some tracing paper and plot all holes out for a better idea of "group" size. Don't know if there are any software programs that can do that and track a specific gun but there ought to be.
 
I'm still waiting on someone to post up a target of a "running group" shot over several months.......

1 shot fired into the same target, at the same distance, every time you go to the range. The variables being you and the weather.

Cold bore shots only.....

I think it would be a better measure of the "good days", "bad days", "too much coffee", and the infamous "all day long" statements.
 
I just carry a half dollar coin with me. If it covers the group, it is good enough for me.....chris3
 
I use the ontarget tds software as well. It does the measuring for you, and saves the bullet hole coordinates in a format that you can then import into Excel.

IMO if you really think about it we shouldn't talk about group sizes, but rather standard deviations. Once you have the standard deviation of the x and y axes you can calculate everything else you would ever want to know. Statistics says you need about 20-40 shots to get a decent idea of what the standard deviation is.

Dryhumor, I've been thinking of doing exactly what you propose. That is, shooting one shot from a cold bore as my first shot at every range trip. That would capture what you can expect in the field. It would capture what happens after you don't clean your gun, just patch and oil the bore, or give it a full brushing and maybe disassemble and clean the bolt, etc...
 
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