What's the official way to measure a group size?


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davek
May 7, 2005, 06:32 PM
Like, is it the distance between the center of the two farthest away holes?

The distance between the outer margins of the two farthest away holes?

Or something else?

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Steve in PA
May 7, 2005, 06:48 PM
I believe its center to center, minus the bullet diameter.

davek
May 7, 2005, 06:55 PM
ARGH! I HATE word problems! :banghead:

UberPhLuBB
May 7, 2005, 07:00 PM
Close.

The measurement is center-to-center.

To get center-to-center, measure the outermost edges of the two farthest holes and subtract the bullet diameter. Measure on the outside of the gray ring the bullet leaves on the paper.

Navy joe
May 7, 2005, 07:48 PM
You forgot the other method which is:
Measure center to center, subtract one bullet diameter, subtract the three rounds that hit the target frame because you want "mechanical accuracy", divide by 2.514 and then post on the internet! :neener:

Standing Wolf
May 7, 2005, 08:30 PM
Measure center to center, subtract one bullet diameter, subtract the three rounds that hit the target frame because you want "mechanical accuracy", divide by 2.514 and then post on the internet!

Well, yeah, sure, but if you divide by 3.187 and 7 and a half 13ths, you can publish it in a gun magazine that sells for $4.95. You're not likely to make a nickel on the internet.

Fair's fair, eh?

M2 Carbine
May 7, 2005, 09:17 PM
If the bullet holes are touching, call it "a one hole group", even if it looks like the target on the right. :D

http://img.photobucket.com/albums/v135/Bell406_206B/Storm.jpg

DonNikmare
May 7, 2005, 10:00 PM
How many rounds would make up a group handgun or rifle?

M2 Carbine
May 7, 2005, 10:24 PM
I think most people call 3 shots a group.

Personally I think 5 or more gives a truer picture of the shooter's and gun's capabilities.

I like about 5 shots for a rifle and 10 shots for a pistol.

Hawkmoon
May 7, 2005, 10:42 PM
Unless you are a writer for one of those aforementioned gun magazines, in which case a group is four shots because they ALWAYS seem to discard a "called flyer."

Sunray
May 7, 2005, 10:57 PM
"...distance between the center of the two farthest away holes..." Exactly.
$4.95??? Geezuz. The gun rags up start at $6, if you can find them. Then the rectal orifi want 15% sales tax. There's two in most provinces. PST and GST. The former is provincial sales tax The latter is our Goods and Services Tax. AKA: The Gouge and Screw Tax.

bogie
May 8, 2005, 11:23 PM
In benchrest group competition, you shoot either 5 shot or 10 shot groups - ten shot is normally reserved for Unlimited class competition.

The groups are shot with a moving and a stationary backer - There may be only one hole in the front target, but there'll be five in the piece of paper that is moved behind the target. And the stationary backer lets you know if any rounds came in from an angle.

The groups are measured center/center of the furthest shots. In reality, they group is measured edge-edge for the largest part of the hole, and then the bullet diameter is subtracted.

Say, for instance, you shoot a ragged hole that measures 0.5" across. You're shooting a .243. You subtract .243 from the largest measurement, and you get 0.257.

jdkelly
May 9, 2005, 06:50 AM
From what I've seen it seems to be:

Inside to Inside (disregarding fliers) divided by two at actual distance plus 50%

So a group that measures 4" (after dropping the 6" flier) shot at 10 yards two handed will become a 2" group shot at 15 yards off hand.:)


Respectfully,

jkelly

brickeyee
May 9, 2005, 11:25 AM
The clamp on attachment for a dial caliper has circles of various diamters scribed on the plastic, and a magnifier in front of everything. Place index hole centered over bullet hole, then gently press device so anchor pin bites a little. Open the caliper and center furthest hole in circle, read C-C distance on caliper.
Repeat as required to find largest C-C reading.
Sinclair had the device, but I do not see it in the online catalog.

pax
May 9, 2005, 12:07 PM
I use a five-shot group and measure center to center. I've never discarded a "called flyer," but I have sat there shooting all afternoon trying to get the best group possible.

pax

wmenorr67
May 9, 2005, 01:10 PM
Who needs to measure? Don't we all shoot dime sized groups at 300 meters? :D

JohnBT
May 9, 2005, 01:38 PM
Yeah, but a dime ain't what it used to be. :scrutiny:

John

MechAg94
May 9, 2005, 01:53 PM
I always thought you shoot 10 or 15 shots, then take the best 5 or 3 depending on what you are trying to get. :)

--I almost always have one or two flyers with pistols. Repeated consistency is something I have to work on.

halvey
May 9, 2005, 02:03 PM
Go to a competition and try to explain to the judges the flyers don't count. Or explain to a deer you would have got him if not for the flyer.

There's no such thing as flyers. Only blown shots. :o

Seriously though, if you are looking for the rifles (and your) potential, then the center to center of the furthest shots.

308win
May 9, 2005, 02:52 PM
Depends on whether you want to replicate it or just pee higher on the bush. :neener:

TechBrute
May 9, 2005, 03:08 PM
UberPhLuBB nailed it, although I'm not sure that's how we do it when we post it on the internet (I can't tell you how many people seem to have .5moa AKs. :rolleyes: )

3 shot groups are for people who can't hold a 5 shot group. 5 Shot groups are credible. 3 Shot groups are not, especially when it started out to be a 5 shot group and got 2 fliers.
:neener:

3 Things matter to me when gauging accuracy and precision:

1st shot POA from a cold barrel
5 shot groups
10 shot groups

I think 10 shot groups the best idea of real-world accuracy, and first shot POA matters if you are actually going to use your rifle (hunting, zombie-busting, whatever.)

wmenorr67
May 9, 2005, 07:01 PM
The military standard when zeroing is 3 shots, check, 3 shots, check and continue until you can get a couple of groups on 3 in row within the black. It only works as well as the guy shooting the rifle.

Standing Wolf
May 9, 2005, 08:57 PM
I use a five-shot group and measure center to center. I've never discarded a "called flyer," but I have sat there shooting all afternoon trying to get the best group possible.

That's a terrible example to set for future gun writers. Excessive honesty does nothing to pump up the reviews of advertisers' products.

Guns_and_Labs
May 9, 2005, 09:17 PM
I think you measure the group size by adding up the antler points on the deer you killed, minus whatever you only wounded. But you get to call a "flyer" if you fell out of the treestand while shooting.

Azrael256
May 9, 2005, 09:37 PM
I hit a British penny at 300 yards one time with a single shot.

'course I'm not going to tell you how many other "single shots" came before it, or whether or not I had given up on the penny and started shooting at something else by then, or the 8-inch halo of "leaded paper" around the penny. Unless there are people around who actually witnessed the event, and that number is dwindling far too slowly, I usually just go with the first part of the story.

Anyway, I usually measure with a coin of various description, or a flattened bottle cap. If the object covers half or more of the hole, I call it in the group. I have a bit of difficulty imagining a 1" group at 75 yards or whatever measure you want to go with. I prefer an object for reference.

When I was a scout, we would shoot something like 30 rounds, and then the instructor would walk out there with a quarter to measure groups. He would tape over every 3-shot group he could make with a quarter. I always kinda thought that was just a bit on the cheating side, but I suppose it works for boy scouts.

pax
May 10, 2005, 12:02 AM
Wolf ~

I know, and that makes me feel just terrible... :D

More seriously, when I started the review-writing gig I decided it would be easier in the long run to tell the truth as I know it. It takes more courage than I expected it would, but not because of any pressure from the advertisers. The pressure comes from inside myself -- pressure to look better than I am, to know more than I do, to pretend I shoot better than I really can. I more than half suspect that that is what drives the dishonest writers, not so much a fear of advertisers but a fear of looking the fool.

pax

We tell lies when we are afraid,...afraid of what we don't know, of what others will think, afraid of what will be found out about us. But every time we tell a lie, the thing that we fear grows stronger. -- Tad Williams

sm
May 10, 2005, 12:21 AM
pax I bet doesn't even own a flowered shirt. :p

I shoot 3 rds and measure center to center no matter what.

Granted I prefer the "Skeet Method" of measuring groups. I fire one slug If it breaks - it's broke. Canteloupes at 21 yds, grapefruit closer in.

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