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Edcnh
Average Member
USA
140 Posts |
 Posted - May 09 2009 : 04:19:17
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| Is there any type of "standard measurement" for measuring group size? I typically measure the outside of the shots which are the greatest distance from each other and then subtract the diameter of the bullet. For example, for a 30 caliber bullet, a measurement of 1.308" on the shots which are the farthest apart would give me a group of 1.308" -0.308"= 1.00". Just curious if many use this method or some other type. |
EDC |
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lefty o
Advanced Member
USA
716 Posts |
Posted - May 09 2009 : 12:18:15
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| you need to use the diameter of the bullet hole in the paper instead of the bullet diameter. |
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Sandwarrior1
New Member
USA
33 Posts |
Posted - Jul 10 2009 : 02:04:25
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quote:
Originally posted by lefty o
you need to use the diameter of the bullet hole in the paper instead of the bullet diameter.
The diameter of the bullet hole out to the very edge of the black around the hole. As the bullet goes through the paper it leaves a black burn-like circle around the holes circumference. It's usually between 1/32 and 1/64th bigger than the hole. |
[url=http://militarysignatures.com][img]http: |
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Bart B.
Senior Member
461 Posts |
Posted - Jul 27 2009 : 21:38:23
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| In Great Britian (and a few other countries) they just measure across the two widest shot's outside edge. No subtracting the bullet diameter. |
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dmsbandit
Advanced Member
USA
1788 Posts |
Posted - Jul 27 2009 : 21:44:13
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Yea Bart, but they drink their beer warm, drink tea instead of coffee, and drive on the wrong side of the road.  |
I don't drink or smoke, I spend my money on gunpowder and gasoline. |
Edited by - dmsbandit on Jul 27 2009 21:46:56 |
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Lee C.
Senior Member
Armenia
226 Posts |
Posted - Jul 29 2009 : 04:01:47
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| Try going to ( on target.com ) they have a free down load for measuring group size. |
Lee |
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fprefect
New Member
USA
36 Posts |
Posted - Aug 10 2009 : 17:28:44
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Measure from the center of the two holes that are physically the furthest apart on the target. That will give you the group size whether you use 3,5,or 10 rounds. Today's best benchrest shooters are capable under good conditions of putting 10 rounds through a hole barely larger than the caliber of the bullet they are shooting, making measuring somewhat difficult. So go shoot a one holer.
fprefect |
In the beginning the Universe was created. This has made a lot of people very angry and been widely regarded as a bad move...Douglas Adams |
Edited by - fprefect on Aug 10 2009 17:37:09 |
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dmsbandit
Advanced Member
USA
1788 Posts |
Posted - Aug 10 2009 : 19:30:20
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| The benchrest circles in my area measure to the outside of the 2 furthest shots and subtract the diameter of the bullet. That's what I've always used, and it seems to give the best measurement. |
I don't drink or smoke, I spend my money on gunpowder and gasoline. |
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dtknowles
Senior Member
201 Posts |
Posted - Aug 11 2009 : 22:50:41
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quote:
Originally posted by dmsbandit
The benchrest circles in my area measure to the outside of the 2 furthest shots and subtract the diameter of the bullet. That's what I've always used, and it seems to give the best measurement.
By best measurement do you mean smallest :-) Bullet holes in paper targets are often smaller than bullet diameter. Measure the diameter of a single bullet hole in your paper target and subtract that instead of the bullet diameter and you will get a better (more accurate) measurement. |
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Edcnh
Average Member
USA
140 Posts |
Posted - Aug 31 2009 : 17:27:21
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| Thanks for the info. |
EDC |
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dmsbandit
Advanced Member
USA
1788 Posts |
Posted - Aug 31 2009 : 19:54:30
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quote:
Originally posted by dtknowles
quote:
Originally posted by dmsbandit
The benchrest circles in my area measure to the outside of the 2 furthest shots and subtract the diameter of the bullet. That's what I've always used, and it seems to give the best measurement.
By best measurement do you mean smallest :-) Bullet holes in paper targets are often smaller than bullet diameter. Measure the diameter of a single bullet hole in your paper target and subtract that instead of the bullet diameter and you will get a better (more accurate) measurement.
I measure to the outside edge of the holes where the "burn" marks are, not the hole. The scoring judges here use a clear template for each caliber. They center the hole under the template and that gives them the outside edge where they measure from. I don't have the template, so I use the "burn" marks. |
I don't drink or smoke, I spend my money on gunpowder and gasoline. |
Edited by - dmsbandit on Aug 31 2009 19:55:51 |
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dtknowles
Senior Member
201 Posts |
Posted - Aug 31 2009 : 23:00:29
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One other way I measure groups is to eye ball the center of the holes and measure center to center and don't subtract anything.
I do this by putting my targets over a blank piece of paper and transfering the centers onto the blank paper then measure the distance between the two marks that are farthest apart.
I had one target this weekend that had 4 aiming points at which I fired four separate 5 shot groups. Largest was 0.44 and the smallest was 0.36 inches. These were shot at 100 yards. Measured this way I am comfortable that I can measure to +/- 0.02, I use an engineering scale that is graduated in 50ths of an inch and I believe I can spot the centers with similar accuracy.
The kicker, I use a common referance and plotted all 20 shots from this target and the exteame spread for the 20 shots was 0.66 inches.
Two of the 20 shots were wide right at 2 and 4 o'clock, they were the only shots that did not cut one hole, excluding those two shots the group was 0.50 tall and 0.32 wide.
This is a used benchrest gun in 6mm PPC, powder charges are thrown, not weighed, standard CCI small rifle primers and unsized brass. Bruno, 68 gr. flatbase double O benchrest bullets. Norma brass with the necks turned. Lapua .220 Russian and FC 7.62 x 39 brass shoot almost as well.
Tim |
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Measuring Group Size
