The group below is a .22 rimfire group and consists of five shots. It has caused some controversy over on the Rimfire thread, at least with one very upset poster who vehemently disputes the measurement between the two widest hole centers of .1915" as show on the calipers.

Please put your eye on the group and provide your best estimate of whether the group is closer to the measurement represented, or more like .300" as the irate poster estimates.

I realize that your frame of reference is limited, but the holes were made by a .22 LR, and the lines on the paper appear to be spaced 1/4". The reference marks on the caliper frame are 5mm, which is .1968".

Well outside looks a touch larger than .191. If you have 2 22 caliber holes that touch then the group would be .224.

Either center to center or outside to outside less one dia.

Looks ok to me

It clearly shows a 22 hole between the centers of the two being measured so that would make me think the group is at least .22 center to center. Not all holes are going to be caliber size though so I would go by the tool reading .191 since it looks like the edges are accurately centered over the holes.

If it is causing a controversy, can the target simply be scanned and posted online and then everyone interested could print it out and use their own calipers to their hearts delight.

It should be a scan, as a camera can conceivably cause a parrallax issue, but then it could just be printed, resized until the bullets measure .22" and measured. Until then everything else is simply an opinion.

How big is the dot you used for an aiming point?

My initial impression is that it's bigger than .191" but I like the scanning, posting, and letting others measure idea.

quote:

Originally posted by 7mmfreak:
How big is the dot you used for an aiming point?

My initial impression is that it's bigger than .191" but I like the scanning, posting, and letting others measure idea.

It's not my target. Go over to the Rimfires section of this AR forum if you want the background.

Not getting into the argument about outside,but to get a true size of the group,you need to subtract about a .20 from outside to outside as a 22 cal. does not make a .224 hole,go to benchrest matches and you will see the bullet does not cut a hole in target paper the size of the diameter of the bullet

Duplicate it 2 more times then we will take best 2 out of 3.

There is clearly a gap between the two outermost holes of the group, so it has to be at least larger than caliber sized. If the edges of both of the outermost holes touched, then it would be exactly caliber sized.

I would flip the paper over and flatten out the hole then it's easy to see the centers

But my groups are measured with a tape measure to the nearest line

No calipers needed when you shoot as bad as I do

As wtb said, the holes are not full bullet diameter. Not even if you look at the way they fit in the caliper tool. I would need to know that true measurement first. IF they were .223, then the group measures more than that.

My 2 cents. It's about .191 center to center. If you use the diameter of the indicater, .22 nominal the caliper is open about the same amount. The center of both outside rounds is with in the middle round.

If someone where so inclined the photo quality is good enough to use On Target to measure all of the groups. The couple I questioned measure near enough on the the screen without going through the hassel.

Edit: Looking at all of the groups there are one or two I'd remeasure but I agree with this one and most of them.

If the lines on the paper are truly 1/4" apart, then the group seems to measure at least that, or something like .27" center to center.

When That caliber is closed, does it read 0.00?

It looks as if the holes in the caliper are different sizes. For instance, if the group was measured with the top set of holes in the caliper, you would have a different reading than the bottom.

Measure the outside to outside with the flat part of the caliper, the deduct the bullet diameter, or use the sharp points of the inside measuring tips to get your outside most measurements of the group then do your math.
I have never used a caliper with those holes in them.

quote:

Originally posted by Kay9Cop:
There is clearly a gap between the two outermost holes of the group, so it has to be at least larger than caliber sized. If the edges of both of the outermost holes touched, then it would be exactly caliber sized.

That was my first observation too.

quote:

It looks as if the holes in the caliper are different sizes. For instance, if the group was measured with the top set of holes in the caliper, you would have a different reading than the bottom.

According to the person who posted the target, the caliper attachments have holes that are .224, .243, and .308, respectively. You are supposed to use the aperture which is appropriate to the caliber you are shooting.

I'm not so sure that there is a gap between the widest two holes. It appears that the "center" shot may have occurred first, folding the paper underneath, then the wider shot came on top of that in such manner that it did not punch the "hanging chad" of target paper which was folded to the rear by the previous shot. When the target paper was pressed from the rear back into its original position, then the small white streak of paper appears to come between the two wider shots.

At any rate, comparing the distance between the caliper attachment blades to the 5mm divisions on the caliper frame, the two distances seem very close, making the .1915 measurement credible. But I'll be the first to admit that accurately "measuring" a picture of a group rather than the physical paper is challenging, at best. That's why I'm hesitant to say the the author's measurements aren't what he says they are.

.191 minus .223 equals -.032 WOW!

Not bad for 20 yards!

All kidding aside, very nice! Looks like dead ground squirrels to me!

PM

Stonecreek.

That measurement is incorrect!

It looks incorrect to me. There is essentially a 3 shot string with the vast majority of the middle bullet showing, plus additional paper on the right side of the bullet impact. I believe it is over .19".

There is no question that there is a gap between the lower left hole and the hole that is to the upper rt from it. In addition that hole is enlarged FARTHER away from the lower left hole. It is impossible for this group to be .191.

Ok maybe I am looking at this to closely...

When I measure for group size I take the outside measurement of the group and subtract the diameter of the bullet to get the size.

How can this measurement be correct if the bullet diameter/individual hole size is .224?

The way those holes seat I would guess about .3 after you take out the diameter. The caliper can't be right as each one of the holes is bigger than that measurement shown!!

I think you need a new caliper! Or use this one correctly; instead of using the outside of the "circle" in the caliper you should be using the straight edge of the guide.

quote:

Originally posted by Mike Michalski:
.191 minus .223 equals -.032 WOW!

I would say that it looks a tad bit larger than .191. However, it looks like the measurement has been done correctly, could be a false reading. To be absolutely sure, I would put a fresh battery in a re-measure.

Let me repeat: This is not my target and is not my measurement.

I only posted it to see if there was a consensus as to its approximate measurement. It seems that more people think it is larger than .191" than think that .191" is accurate. I neither agree nor disagree, contending only that it can't be accurately measured by only a photo due to a couple of factors which can only be determined by looking at the physical target. In my experience it can be very difficult -- and deceiving -- to locate the exact edge of holes made by round-nose bullets, particularly .22 rimfires. This is one reason that I have a bit more trust in measuring from the centers -- however, measuring from the centers is of course impossible when the groups are as small as this one.

Case in point -- at least some posters believe the two holes measure (whether accurately measured or not) at not the two widest holes. Again, I'm not at all sure about that since the caliper attachment partially covers a disputed hole; but I've got to assume that the measurer measured both holes and determined the one illustrated to be the further.

It would be interesting if the owner of the target could show the group from the reverse side, which might shed a bit more light on it.

If the 2 holes bracketed by the calipers are touching edge to edge then the group should measure .224" roughly center to center.
They would have to overlap each other (which it appears they are not) to be less than .224".
What I see is an admirable group shot at an unknown distance.
Why the big meltdown over .0325" its not like he's shooting in a tournament or something, isn't this all for fun??

Looks accurate.

Probably would help if the light source was in the center so that there would not be any shadow affect, so you could see the outer circle he/she is using as there reference point.

So I played with On Target and centered up the shots over the approximate centers, knowing that the smudge of a .22 round nose is smaller than the bullet size and came up with .219 or .222 inches for the group doing it twice to see how it would come out. Measuring the smudge alown may be .191. I may play with the other groups to see if they are as different as I think they are.

Sam: Not questioning your results, but how did you correct the image to actual size? Did you use the 5mm hash marks on the caliper, or what?

I thought that 22 rimfire's were .223 in diameter?

That said it still looks like a small group.

Using the built in measurement setting in the program I set the distance of the points of the ".22" hole to .224 and centered .22 caliber holes generated by the software over the impacts. It was very similar to using an Eagle Eye to score targets after I established the .224 measurement. There are some sources of error that can be attributed to minor loss of focus, not being perpendicular to the group, etc.. If I had to pick what may be a consistant error it may be measuring to the edge of the smudge which is less than the diameter of the bullet. I tried to post the .jpg but failed. I will try again after work.

He needs to reset the caliper to zero. There is no way IMHO that reading is correct

Like I said just like using an Eagle Eye.

Great illustration, Sam!

Where you placed the .224 circles illustrates both of the wider shots almost exactly in tangent with the shot on the left, which, of course, is a ~.224 group.

As I mentioned earlier, I think that the tag of white paper that is visible "in the middle" has some people confused since they assume that if it is still there it was not hit by a bullet. Of course, this is wrong since the passage of the bullet doesn't destroy the paper, it merely displaces it so that "tags" like this one will reappear when the paper is pressed back into its former position from the rear. Your .224 circles meet exactly on top of this tag of paper, which appears to be the appropriate place to me.

Your illustration assumes that the measurer did not take into account that the apparent bullet holes from a .22 RF are in fact a bit smaller than the actual impact. It might be arguable that your spacing is too wide, but even so, the group measurement is a maximum of .224", and could be a tad smaller.

Thanks again for the very enlightening illustration.

You're welcome.