Need proper way to measure shot groups

[ddboomstick]

And I figured this would be the place to ask. I want to start keeping closer track of my groups with different ammo. My question is: What is the proper way to measure 5 shot groups? Do I put a circle around all 5 and measure the diameter? Do I count all 5 or do I dismiss one as a flyer? Or What? Thanks!

 

[PPCSHOOTER]

COUNT ALL 5 SHOTS. MEASURE LARGEST OUTSIDE MARK TO OUTSIDE MARK AND SUBTRACT THE WIDTH OF THE BULLET. THIS IS THE EASIEST WAY. MOST MEASURE CENTER TO CENTER OF THE FARTHEST APART BULLETS. BUT IT IS HARD TO FIND THE DEAD CENTER OF A ROUND HOLE. JP

 

[BoDog]

PPCSHOOTER has it right, buy a set of digital calipers from some place like Harbor Freight. Measure the distance between the exteror of most distant holes and subtract the bullet diameter.

 

[brucev]

I would simply add, measure the size of a bullet hole in your target. Some paper allows a clearer more measurable bullet hole. Also shooting lead bullets in a handgun will leave a very much more measurable hole in the paper. Measure 5 to 10 bullet holes. Take the average as your norm. In my experience shooting vintage military rifles in practice and matches, a .30 bullet produces a hole/shadow in the paper of between .25-.28 outside to outside. I measure the group from the outside edge of the widest shots and then subtract the nominal width of a bullet. Another method is simply to measure edge to edge, i.e., pick the bullet hole farthest to the left. Set your caliper/ruler on the right edge of that bullet hole. Now measure to the farthest bullet hole on the right. Measure to the right edge of that bullet hole. It might not work for registered benchrest competition, but it will give you a very good basis for comparing your results for that particular trip to the range. As well, good record keeping will allow you to compare the effectiveness of various loads in a rifle/handgun with respect to method of firing, position, ambient conditions, etc. JMHO. Enjoy your time at the range! Later today I hope to be able to spend some time myself shooting my M-28 and M-625. Sincerely.

 

[ddboomstick]

Thank you all very much!