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i have a buckmark that i will be trying to find the tightest grouping of ammo that works best in it..aside from "looking" at the groups and decideing which one is best...how do i measure the group...i don;t want big technical measurements..just like with a ruler and some simple measurements to get an idea ....thanks
 

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Another way to measure groups is to lay your target down over a piece of paper. With a pen or pencil mark a spot in the middle of the two farthest bullet holes (this is a guess as to the center so the accuracy may not be all that great but will give you a good idea). Just take a ruler or whatever your measuring with and measure the distance between the dots you made. That will give you a rough center to center idea.
 

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While it will "open up" your groups, you should remember that most ammo does not punch a same diameter hole in a target. Measure a single hole in a target and you'll see what I mean.

For .22LR, I subtract .19" from an outter edge to outter edge measurment to calulate a center to center group size.

Different bullets punch different size holes, but untill you can get .22LR wad cutters, the hole in the paper will be smaller than the bullet.
 

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Keep in mind that measuring a .22 bullet hole from grey edge to grey edge will be less then .224". Out of my barrel that measurement will be around .208". Using .224" will likely give you a smaller group size then true center to center measurement would produce. The best way to get a true measurement is to measure some single shot bullet holes out of your barrel, and subtract that number from the outside measurement of your group.
 

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The thickness of the paper will determine how much you need to subtract. For targets on regular copy paper shot with a 22lr subtract .207 for bullet diameter. On thicker carbon stock paper subtract .211 for a bullet diameter. For 17HMR on copy paper subtract .155 for bullet diameter. For carbon stock paper subtract .159 for bullet diameter. This is pretty dang close from what I have found on average for differences in the bullet diameters of these bullet holes made on these different paper thicknesses.

Also a lot of guys will just measure from the outside edge of actual hole that the bullet makes from the farthest two shots. That's not correct but it will work as long as you subtract for the bullet diameter with the same process of measuring. The correct way is to measure the outside edge of outer black lead smear ring on each of farthest two bullets holes in the group. The same is true for measuring a single bullet hole. You measure a bullet hole from outer black lead smear ring to the opposite side black lead smear ring. This is why some guys get the small bullet diameter for a 22 bullet because they only measure the size of the hole that the bullet makes instead of measuring from lead ring to lead ring.

I have found the thicker the paper used, the bigger the hole that the bullet will make. The opposite happens with the thinner the paper used. I guess the reason for this is the thicker the paper is the longer the bullet is actually in contact with the paper and thus allowing bullet to actually make a bigger hole.

So in other words your bullet diameter will be .013 to .017 smaller(depending on the thickness of paper that is used) than the true actual bullet diameter you are shooting. If you are shooting thicker paper than carbon stock paper, your bullet diameter will actually print a bigger hole more closer to the true diameter of the bullet.

Keep in mind that different brands of ammo may have +/- a few thousandths for bullet diameter or even from same brand from box to box there can be a very small difference. So the best way to know for sure is to shoot a particular brand on the actual paper being shot and measure the diameter of the actual hole that it makes.

Your mileage may vary on this. But for the most part this method will be fairly accurate for subtracting for bullet diameter.

Brad
 

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Does anyone else find it amusing when people measure ragged holes in paper to a precision of .001 inch?

Maybe I am just jealous that my eyes are not that good anymore. :)

Jerry
 
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