How do YOU measure groups?

[Tim]

This pic is a 5 round group I shot today. Got to talking with another shooter about group size, and general stuff.

I measure the group as shown, furthest linear distance (.636”, measured at the black ticks), then subtract the bullet diameter (.264”) to get a group size (.372”).

He was arguing the true group size is the .636” alone.

I like my math better.

Who’s right?

 

[Trevillian]

"center to center" of the outer most bullet holes is how I see it. But I personally claim outer edge to outer edge

 

[NKD]

I thought it was center to center.

 

[Tim]

I thought it was center to center.

"center to center" of the outer most bullet holes is how I see it.

That’s basically the same as edge to edge minus bullet diameter. But when your group is “one hole” it can be hard to find an individual center.

 

[foopid stucker]

center to center. compensates for any difference in bullet caliber.

 

[Tim]

center to center. compensates for any difference in bullet caliber.

Why would you measure groups from different calibers?

If you’re talking about a variance from bullet to bullet within a “caliber”, I’d think the margin of error would be less than you’d find trying to locate “center” of two different strikes within a group

 

[JustKeepSwimming]

That is just damn fine shooting Tim. I wouldn't care less what it measured!

 

[GymB]

Time to move the target back from 20yards.

I’ve always been told to do it exactly as you do.

Why would you measure groups from different calibers?

If you’re talking about a variance from bullet to bullet within a “caliber”, I’d think the margin of error would be less than you’d find trying to locate “center” of two different strikes within a group

I think he means if you shoot .308 and I shoot .223 you’re at a disadvantage if we measure from outside to outside without adjustment, but if we subtract a bullet diameter then the groups are directly comparable.

 

[Tim]

That is just damn fine shooting Tim. I wouldn't care less what it measured!

Thanks, I’m starting to figure out this new Tikka TAC A1.

5 x 5 shot strings @ 100 today averaged .525” (after subtracting bullet diameter)

3 x 5 shot strings @ 200 averaged 1.6”

Not as good as the Savage I sold, but still working on load development.

 

[Schattenreiter]

Here is the official word from Brownells.

 

[REELDOC]

If it fits in an 8" paper plate at a hundred it's good to go.

 

[Catfish]

The way I shoot I usually just pace them off. Sometimes I get lucky and I can use a tape measure.

 

[nature boy]

When u shoot groups like this at100 yards u good to go woooooooooo

 

[OldNascar]

Center to center, otherwise the smallest bullet diameter has the advantage. Measuring the outermost of the group only works when all comparisons are of the same caliber.

 

[cubrock]

Center to center, otherwise the smallest bullet diameter has the advantage. Measuring the outermost of the group only works when all comparisons are of the same caliber.

Center to center here, to. There are a couple different ways to do this to arrive at the same group size.

 

[P01135809]

 

[Howland]

I tried measuring from the outside edge of the furthest holes then subtracting bullet diameter but it's tough to estimate where the exact edge of the bullet hit. Much easier and more accurate to measure center to center. I just remeasured twelve groups and realized the outside to outside method was giving me consistently smaller groups than reality.

 

[GymB]

I tried measuring from the outside edge of the furthest holes then subtracting bullet diameter but it's tough to estimate where the exact edge of the bullet hit. Much easier and more accurate to measure center to center. I just remeasured twelve groups and realized the outside to outside method was giving me consistently smaller groups than reality.

If you can’t find the edge of a hole consistently, how do you find the center?

 

[CZfool68]

Usually with a yardstick.

 

[Average Joe]

I use the same technique, measure outside to outside then subtract bullet diameter. Glad you're figuring out the Tikka @Tim. Helps me not feel too guilty about taking such a great rifle from you.

 

[Mikew]

Doesn't matter, if the target was somethings head it's probably dead from the first round.

 

[Donnie D]

I don't measure my groups, because when I do, I get very depressed.

 

[Bailey Boat]

You can measure a group in whatever manner makes YOU feel better. It's all about how YOU feel and what you want it to say.

You can also subtract the diameter of the caliber when you shoot with a timer. That's right, whatever makes YOU feel good....

 

[Trevillian]

Center to center-ish


Outside to outside


That's a Ruger American all weather compact in 308 with factory ammo at 100yds.

I only claim it'll do under and inch if I do my part. It may do better now with my hand loads

Oh. Always 5 round groups.

I also know of some who do 5 then measure the smallest 3

 

[BatteryOaksBilly]

Subtracting the bullet diameter from your above outside measurement gives the same group as the one measured from centers. Not much to debate is it?

 

[Trevillian]

Subtracting the bullet diameter from your above outside measurement gives the same group as the one measured from centers. Not much to debate is it?

Exactly

 

[Gator]

If the O/D of the bullet cuts the scoring ring on the target between the 9 & 10, do you count the score as a 10 or do you subtract the diameter of the bullet and give yourself a 9?

Seems to me the whole bullet counts, not just the pointy part on the front end.

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[bigfelipe]

If the O/D of the bullet cuts the scoring ring on the target between the 9 & 10, do you count the score as a 10 or do you subtract the diameter of the bullet and give yourself a 9?

Seems to me the whole bullet counts, not just the pointy part on the front end.

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Scoring vs grouping... Different measurement systems...

 

[BatteryOaksBilly]

If the O/D of the bullet cuts the scoring ring on the target between the 9 & 10, do you count the score as a 10 or do you subtract the diameter of the bullet and give yourself a 9?

Seems to me the whole bullet counts, not just the pointy part on the front end.

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Here the Shooter Always gets the break.