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

[davek]

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?

 

[Steve in PA]

I believe its center to center, minus the bullet diameter.

 

[davek]

ARGH! I HATE word problems! :banghead:

 

[UberPhLuBB]

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]

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!

 

[Standing Wolf]

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]

If the bullet holes are touching, call it "a one hole group", even if it looks like the target on the right.

 

[DonNikmare]

How many rounds would make up a group handgun or rifle?

 

[M2 Carbine]

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.

 

[Aguila Blanca]

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]

"...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]

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]

From what I've seen...

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]

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]

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]

Who needs to measure? Don't we all shoot dime sized groups at 300 meters?

 

[JohnBT]

Yeah, but a dime ain't what it used to be.

John

 

[MechAg94]

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]

flyers

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.

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

 

[308win]

Depends on whether you want to replicate it or just pee higher on the bush.

 

[TechBrute]

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. )

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.


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]

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]

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]

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]

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.