Redlg155
Member
Fellow Shooters,
I've pretty much always measured the entire group size when figuring out a group. Nothing scientific, just if it all fit within a 1" square I called it a 1" group. Perhaps I've been short changing myself!
Anyway..I've done some cuttin n pasting from this site. http://proveit.www8.50megs.com/measuring/measuring.html Does everyone use this method?
The best way to measure groups that I'm aware of is the caliper attachment sold by Sinclair for about $50. You can get a usable dial caliper from Enco for about $15. Of course not everyone wants to spend $75 just to measure groups, so here is the method that I recommend. A dial caliper makes things easier, but a precision ruler will work fairly well also.
What we want to determine is the center-to-center distance between the two farthest shots of each group. The method here is to measure the maximum distance between the outer edges of the two farthest shots and then subtract the diameter of a single bullet hole, which gives the center- to-center distance.
First, turn your target over and push the jagged parts of the paper around the hole back to their original positions as much as possible. Turn the target back over and notice that the holes look rounder and are more well defined.
Second, you need to determine the typical diameter of a bullet hole. The bullet hole is rarely as large as the bullet, and its size varies depending on the ammunition used, the thickness and type of paper used for the target, the target backstop, and other factors. Actually, what is usually measured isn't the hole, which is often jagged and irregular, but instead the ring of fouling that is left by the bullet as it passes through the paper. This ring is usually the most consistent feature of the bullet hole, but you can base your measurements off whatever you like as long as it is consistent. Dirty ammo makes for the easiest groups to measure. I've seen rings as small as .18", so don't assume that your holes are .22".
Find an individual bullet hole and measure the diameter of the fouling ring as shown below. Measure a few other holes and take the average of the measurements. This is the typical bullet hole diameter. If you are such a good shooter that you don't have any individual holes, you'll need to remember to shoot a few into the sighter box so you'll have something to measure.
Third, find the largest distance that you can measure on the group. Measure to the same feature on the holes or fouling rings that you used to measure the size of the individual holes. On round groups it may not be obvious which two holes are furthest from each other, so make as many measurements as necessary to make sure you have the largest distance.
Finally, subtract the typical bullet hole diameter from the overall group size to get the center-to-center distance. Round to the nearest hundredth and write this number above the group.
---------------------------------------------------------------------------------------------
Good Shooting
Red
I've pretty much always measured the entire group size when figuring out a group. Nothing scientific, just if it all fit within a 1" square I called it a 1" group. Perhaps I've been short changing myself!
Anyway..I've done some cuttin n pasting from this site. http://proveit.www8.50megs.com/measuring/measuring.html Does everyone use this method?
The best way to measure groups that I'm aware of is the caliper attachment sold by Sinclair for about $50. You can get a usable dial caliper from Enco for about $15. Of course not everyone wants to spend $75 just to measure groups, so here is the method that I recommend. A dial caliper makes things easier, but a precision ruler will work fairly well also.
What we want to determine is the center-to-center distance between the two farthest shots of each group. The method here is to measure the maximum distance between the outer edges of the two farthest shots and then subtract the diameter of a single bullet hole, which gives the center- to-center distance.
First, turn your target over and push the jagged parts of the paper around the hole back to their original positions as much as possible. Turn the target back over and notice that the holes look rounder and are more well defined.
Second, you need to determine the typical diameter of a bullet hole. The bullet hole is rarely as large as the bullet, and its size varies depending on the ammunition used, the thickness and type of paper used for the target, the target backstop, and other factors. Actually, what is usually measured isn't the hole, which is often jagged and irregular, but instead the ring of fouling that is left by the bullet as it passes through the paper. This ring is usually the most consistent feature of the bullet hole, but you can base your measurements off whatever you like as long as it is consistent. Dirty ammo makes for the easiest groups to measure. I've seen rings as small as .18", so don't assume that your holes are .22".
Find an individual bullet hole and measure the diameter of the fouling ring as shown below. Measure a few other holes and take the average of the measurements. This is the typical bullet hole diameter. If you are such a good shooter that you don't have any individual holes, you'll need to remember to shoot a few into the sighter box so you'll have something to measure.
Third, find the largest distance that you can measure on the group. Measure to the same feature on the holes or fouling rings that you used to measure the size of the individual holes. On round groups it may not be obvious which two holes are furthest from each other, so make as many measurements as necessary to make sure you have the largest distance.
Finally, subtract the typical bullet hole diameter from the overall group size to get the center-to-center distance. Round to the nearest hundredth and write this number above the group.
---------------------------------------------------------------------------------------------
Good Shooting
Red
