# Measuring targets



## Savage260 (Oct 21, 2007)

What way do you all measure your targets. I looked at some stuff on Steve's Pages, but it had a bunch of ways to do it, but most said they were only good for a certain aspect. I have been saying my groups are 1" if all 5 shots will fit in a 1" box, but now I am pretty sure that is not correct. Thanks for any and all replys!

Laite


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## ac700wildcat (Oct 30, 2006)

I usually will measure how far apart the two furthest shots are from the outside of each hole. And then you can subtract the width of one hole to get your center to center. Either that or just put whatever you measure with in the center of one hole and measure to the center of the other hole. I think the first way is how they actually would do it in competitions.


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## Jaybic (Sep 8, 2005)

I agree with wildcat,

As I understand, its outside to outside of the farthest two holes and then subtract the bullet diameter.

If the farthest two shots are .936in and you are shooting a 22-250, which is .224 bullet diameter it is:

.936-.224=.712 which is just under 3/4 of an inch

I might be wrong but thats the formula I think.

If your getting 5 shots in less than a 1 inch square, you can certainly call it shooting under an inch groups. Probably closer to 3/4 inch which IMHO is plenty good shooting to me. :beer:

jaybic

Jaybic


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## Savage260 (Oct 21, 2007)

thanks for the replys, but now I have another question. That way to measure works, but it is just a linear(if that is the right word) measurement. If I have 4 shots in .731 from left to right it comes out to .507, but the 5th hole is about centered on the other 4, but slightly above. How do I take that shot into account?


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## Jaybic (Sep 8, 2005)

If I am understanding the question correctly, It will not matter.

It only matters from from the two farthest apart bullet holes no matte how many shot group it is. If you shoot a two shot or a 50 shot group, just pick the two bullet holes farthest apart and measure them and subtract the bullet diameter and that is your group size. You essentially ignore every single bullet hole except the 2 that are farthest apart no matter whether they fall on that "linear line" or not. The "shape" of the group does not matter.

Again, I may be mistaken and if so I apologize and I hope some one points us both in the right direction but I am almost sure that this is how its done for "official" measurements.

Good Luck,

Jaybic


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## Savage260 (Oct 21, 2007)

You essentially ignore every single bullet hole except the 2 that are farthest apart no matter whether they fall on that "linear line" or not. The "shape" of the group does not matter.

Jaybic, that is exactly what I am getting at. I want to measure the group, not just a line. If there were .507" and the 4 holes made a box with one shot in the center 0 0
0
0 0

some thing like that it would be a worse group than 0000
0
even though the farthest distance was still .507.










this is the target I am wondering about, how do I take into account each shot so I know what kind of group I am getting? Ignore the 0's they don't show up on the post the same way they did when I typed this out.


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## neb_bo (Feb 3, 2007)

why does it matter that one is not in line? the only thing that matters is the total distance of the two worst shots.


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## cwoparson (Aug 23, 2007)

It's the diameter of the group you're looking for.


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## whitehorse (Jan 28, 2008)

cwoparson said:


> It's the diameter of the group you're looking for.


exactly, easiest way is as stated, only tweek it just a little... instead, Find 2 furthest, measure outside of one, to to the inside of the other. Then you don't have to worry about subtracting, gives quick answer.. butt, yes, diameter is what we're shooting for!!


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## Savage260 (Oct 21, 2007)

> why does it matter that one is not in line? the only thing that matters is the total distance of the two worst shots.


I guess I was thinking in terms of accuracy. Distance of each shot from the intended target. The "worst" of the 5 shots would be the 2 farthest to the right. But if you only measure the 2 shots farthest apart it doesn't give an accurate reading on your "group" only the straight line distance between those 2 shots. I guess if that is how most people measure it, I am ok with that. I just didn't want to get into a situation where I say I got a half inch 5shot group then some one looked at the target and said, no that isn't right.


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## neb_bo (Feb 3, 2007)

yeah, that is how its measured. when you are talking about grouping, you are only concerned with the ability of the rifle to place shots in the same spot, not the actual placement of the shots in relation to point of aim.


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## ac700wildcat (Oct 30, 2006)

You don't actually subtract the diameter of the actual bullet after you measure to the outsides. The reason being that when you shoot thru paper it doesn't actually make a hole as big as the bullet, it kinda folds the paper out of the way. If you measure the size of the holes in the paper it will show this. If you just measure like five holes and average them, then that is what you would subtract. Also the hole size will probably depent on the type of paper used in the target as well as the bullet type.

Matt


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## johngfoster (Oct 21, 2007)

I try to measure from the outside of one hole to the same side of the furthest away hole. I agree that if you measure outside to outside and then subtract bullet diameter, you get a falsely small group. Some of my 22-250 holes in paper only measure 0.200" diameter, this from a bullet that was 0.224".


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## Jaybic (Sep 8, 2005)

John,

I can see what you are talking about but am not sure I agree or I might just not be understanding correctly. I know that depending on the paper you shoot it may appear to be an undersize hole because the tip of the bullet tears the paper before the actual bullets full diameter passes through the hole and the paper is then "folded back" like was said earlier but that does not reflect the bullet size, it kinda snaps back to the smaller diameter. The actual bullet size is where white paper meets obvious lead colored paper which is the "folded back" part.

It is for the same reason that in the photo above by the OP the group is actually smaller that he is stating(awesome!) because he is using "shoot n C" targets and is measuring from on the "yellow" rather that the actual edge of the bullet hole(look at the left edge of the dial caliper-its not up next to the exact edge of the bullet hole like the right one is) so it is giving a group larger that it really is. Shoot N See targets are nice but do not lend themselves to accurate group measuring.

Just my .02 but if a person used cardboard with a small aiming point...ie 1/2 inch-1inch orange dot and site in so that the group hits about 1.5 inches high on the cardboard, it gives very nice, sharp, round bullet holes with out that paper fold over(falsely small) or the shoot n see oversize holes(falsely large by design so you can see them from the bench).

It will make measuring groups much more accurate and you will not get bullet holes or groups smaller than the bullet you are shooting.

Again, I might be wrong here but just to be sure I am going to drop by the benchrest.com forum and ask how they measure and I will relay what I find out but as I understand it, when they say they shot a group that measured .033 that means it was .033 larger than the five .224 bullets they shot through that same hole.

They have all the current records posted there and they are amazing! I just found the site about a week ago and there is much to learn if you want to know about shooting groups and accuracy and all things reloading and gunsmithing.

Sorry for the long post.

Take is easy, :beer:

Jaybic


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## iwantabuggy (Feb 15, 2005)

I measure the two holes that are farthest apart and subtract the bullet diameter, just like many of you do. If someone wants to knit-pick it beyond that, it is okay with me. But I likely wouldn't show them any more targets. The only time it would matter is if you were in a competetion. Even then, as long as all the measurements were made the same way, it wouldn't matter.

Laite319,

I'd call that group of yours a might fine one.  You got a nice shooter and know how to use it.


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## Savage260 (Oct 21, 2007)

> I'd call that group of yours a might fine one. You got a nice shooter and know how to use it.


Hey, thanks. The rifle is great, it will out shoot me every time. That group was just luck, I think. I have been shooting for groups with about 7 different powders, and only 2 so far have shot like that. If I zoomed out and got the rest of the groups on the target you would think I just learned to shoot last week!!!

Thanks to every one who posted. The info was greatly appreciated.


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## cwoparson (Aug 23, 2007)

> It will make measuring groups much more accurate and you will not get bullet holes or groups smaller than the bullet you are shooting.


Seems to be some confusion here. It is possible to shoot a group smaller than the caliber you are shooting. Can you shoot a half inch group with a 45-70? Of course you can. Center to center measurement is the way it is done. Doesn't matter about the outside edge of the bullet. It is where the center of the bullet strikes the target that tells you how accurate your group is. The center of the bullet hole will always be accurate regardless of how the paper folds back around the edges. Measure center to center and that diameter length is your group.


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## Jaybic (Sep 8, 2005)

Hey guys,

I went to benchrest.com and they did have the question posted: "How do you measure groups?" (please feel free to check it out for yourself under "forums")

I learned alot and man, those guys are SERIOUS about every little detail! According to professional/competition bench shooters, groups are measured from the outside edge of the farthest apart two bullet holes and then the bullet diameter is subtracted to yield the actual group size. Apparently this is also done by a panel of people and not just one person and then they agree on a number because everyone seems the get a number that is a few thousands of an inch different.

It was also suggested that a person set their digital dial caliper to .224 or what ever bullet size you shoot and then zero it and you dont have to subtract anymore. Its already calculated in the number.

It also mentions that it is not uncommon for bullets to leave holes smaller that their original unfired diameter but they dont say why. My guess it that maybe a bit of bullet jacket is shaved off going down the barrel(explains copper deposits in the barrel?) or due to velocity, the bullet is actually "stretched" out when fired due to atmospheric conditions or wind resistance or what ever but I am totally guessing here. Maybe I should post this there and see what the bench guys have to say?

Anyway as for 1/2 inch groups with a 45-70, you surely can shoot a .05 in group with a it, and measuring outside to outside minus bullet diameter will still give the same measurement as measuring center to center. It has to. The difference is that the outside edge of a bullet hole is clearly defined on the target but to find the "exact center" of a bullet hole is simple guessing because its not there. Thats fine for getting close and hunting grade accuracy but if a person wants to split hairs and do it the "official" way, that is how its done according to the BR guys that shoot NBRSA and other competitions.

Anyway, check it out if you like. They have taken reloading and ballistics and everything we strive for here to the next level. Great info!

Take it easy all, :beer:

Jaybic


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## cwoparson (Aug 23, 2007)

> and measuring outside to outside minus bullet diameter will still give the same measurement as measuring center to center. It has to. The difference is that the outside edge of a bullet hole is clearly defined on the target but to find the "exact center" of a bullet hole is simple guessing because its not there


Agreed and I'm pretty sure that's what I said except for the center to center not being easy to find. I would submit to you that center to center is easier to find than the outside diameter because the outside of the bullet hole is not easily defined. Paper fold back/rebound or lube smear will alter the outside dimension. I think if you talk to those guys at the bench rest sight you will find a lot of them use a bullet plug to determine the bullet hole. The backing on the targets they use will form perfectly to the bullet hole where as the attached paper target will not. Using plugs will give them a true measuring point. Though some bullets, depending on manufacture will not be of a standard diameter of .224, some may be .223 or .2245 as a example, but all plugs used are .224 for fairness. That's probable what they were talking about on different bullet sizes as a bullet will not stretch but may bump up to a larger and measurable diameter but that is usually related to lead bullets only.

Have you looked at some of the scores of those over at that forum? Some .105's up to .200 is not uncommon for a few of the experts.

On the caliper adjustment I don't see how that would work on a dial caliper but I guess it would work on a digital caliper where one could set a negative .224 reading.


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## Jaybic (Sep 8, 2005)

Cwoparsons,

I think maybe you and I are pretty much saying the same thing but in different enough terms that It appears that we disagree. Sorry If I misunderstood. I am not convinced about it being easier to find a defined center than a defined edge but I think you are right on something. I believe it depends on the paper or target you shoot. I often shoot cardboard with a small 1 inch or 1/2 inch aiming point on it and sight in so I hit high on the cardboard which leaves very nice sharp-edged bullet holes. If I just shoot paper stapled to a wood target backer the holes are sloppy on the edges and that is where I would agree with you and use center to center measurements. I like the idea of using a bullet plug also. That, I would think that would completely eliminate the issue altogether. :beer:

What do you think, do bullets get a little bit of shaved off jackets on the way down the barrel to account for that smaller that the original bullet size hole? That seems plausible to me.

I dont know anything about plain lead bullets either and I was just crazy-guessing about the stretching thing. BTW, the dial caliper thing was on a digital set up to .224 in the negative but i dont see how you could do it with a regular one either.

Yeah, I did look at some of those groups and that is crazy to me that they shoot that well. In some cases they are shooting groups so small that you could shoot a .45 cal hole in their targets and they could thread .224 bullets thru the hole and never touch the sides of it. 

Good luck,

Jaybic


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## cwoparson (Aug 23, 2007)

:lol: Yes, we are saying the same thing.


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