Making A Group Gauge

Every gun writer, competition shooter, reloader, and hunter loves to brag about how small a group his favorite rifle and load will shoot. Sometimes I listen to those stories and want to ask to see some of those groups, but whether they really exist or not doesn’t matter. When I go to the range I like to try out new loads, bullets, and powders just to see if I can improve on my own personal record with a gun. To do that, groups must be measured. One of the fastest ways I’ve found to do that is with a group gauge.

A group gauge is a clear piece of plastic with circles etched into it representing 1/2, 1, 1 1/2, and 2 inches Bore a hole in the center of the plastic piece. in diameter. To use, the gauge is laid over the target and centered on the group being measured. By moving the gauge so the inner edge of the farthest holes apart are just touching the same circle, the gauge indicates the size of the group. However, before you can use the gauge you need to have one so let’s get the materials together and make it.

You will need a sheet of plastic 1/16-1/8" thick and large enough to cut a 4"x6" rectangle out of it. For tools, you’ll need a sharp knife to cut the plastic, a compass to scribe the circles, a ruler to set the compass, a black marker, paper towels, and mineral spirits. Cut a 4"x6" rectangle from the plastic, locate the center, and use a knife tip or a drill to make a small hole. This will be the center of your gauge.

Set the compass to 1/4" between the metal point and the pencil tip, place the tip of the pencil or lead in the hole, and use the metal point to scribe a circle. Work slowly when scribing the circles, cutting small arcs at a time. Go over the arcs and then the complete circle several times to make the lines as deep as you can. This first circle will be a half-inch across. Next, set the compass to 1/2" and repeat the procedure for a one-inch circle.

Then again with the compass set at 3/4" (1 1/2" circle) and at 1" for a twoinch circle. This creates four scribed circles to indicate your group size when placed on the target. If you normally shoot black bullseyes, leave the scribed circles as they are. If you shoot red or similar lighter colored sight-in targets, the next step is to blacken the scribed lines so they stand out against a lighter background. To darken the scribed lines, take a permanent market and trace it over the lines.

I also scribe the numbers 1, 2, and 3 on the gauge so as to indicate the size of the circle to their right. It isn’t necessary to

be neat when tracing the lines but do try to get ink all the way to the bottom of the line. Once the lines are blacked in sufficiently well, moisten a paper towel with mineral spirits and rub off the ink that remains on the surface of the plastic. As long as the paper towel is just damp and not soaked, it will leave the ink in the bottom of the scribed lines and make the lines easy to see. In use, lay the gauge on your target over the group.

Center it so that the inner edge of the two holes farthest apart in the group touch or are in the same proximity to the smallest circle I like to space mine so they are 1/2, 1, 1 1/2, 2, and 3-inch circles. You can make as many as you like spaced for your guns and range. The scribed numbers represent the size of the circle to the right. Neatness doesn’t count, just be sure the ink covers the bottom of the scribed line. they can both be near. This lets you easily ascertain the approximate group size.

For this project, a picture is truly worth a thousand words so refer to the illustrations. This is an easy project to make a gauge that I find helpful. AG Far In this case, the two holes farthest apart are both inside the 1" circle, giving usa group size of about 7/8". That way it is handy whenever I want to log accuracy results.