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How do you measure your groups?

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Gil P. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gil P. Quote  Post ReplyReply Direct Link To This Post Topic: How do you measure your groups?
    Posted: April/03/2013 at 15:14
The way I do it is I measure the two furthest bullet holes away from each other edge to edge, and then I subtract .308 (bullet diameter) from that number to get a center to center number. I am using electronic calipers to measure my group sizes.

I am asking because, I have seen other 5 shot groups that measure .5 inches (shot with an unknown caliber) that look almost like all the bullets are going into the same hole.

So, how do you measure your groups? And, what is the standard way of measuring them? I think I might be measuring mine incorrectly.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Urimaginaryfrnd Quote  Post ReplyReply Direct Link To This Post Posted: April/03/2013 at 16:01
Center hole to center hole is the most accurate measurement. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote budperm Quote  Post ReplyReply Direct Link To This Post Posted: April/03/2013 at 16:17

+1!

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Mike McDonald View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike McDonald Quote  Post ReplyReply Direct Link To This Post Posted: April/03/2013 at 17:29
I generally cover them with a #2 pencil eraser.
If I can see anything outside the eraser I know I've made an error and must practice a while longer. Bandito
 
Gil your way will work fine.
Center/Center also works well.
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Gil P. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gil P. Quote  Post ReplyReply Direct Link To This Post Posted: April/03/2013 at 19:50
Originally posted by Mike McDonald Mike McDonald wrote:



I generally cover them with a #2 pencil eraser.
If I can see anything outside the eraser I know I've made an error and must practice a while longer. Bandito
 
Gil your way will work fine.
Center/Center also works well.
If I can see anything outside the eraser I know I've made an error and must practice a while longer.

Haha very funny, but I don't think im quite there yet.

Thanks for the help guys, I suppose the one hole looking group I saw wasn't actually measured. They simply stated a guesstimated size and it was probably a lot smaller than stated.

On a side note, I sent my rifle to Phoenix Custom Rifles to have a New barrel put on, barrel channel opened, new recoil lug installed and some action truing done. I should be getting it back in a about a month (maybe less). Then, with practice I can see my groups REALLY start to shrink! Ill post pictures for you all when it gets here.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote stickbow46 Quote  Post ReplyReply Direct Link To This Post Posted: April/03/2013 at 22:25
+2 center hole to center hole.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote budperm Quote  Post ReplyReply Direct Link To This Post Posted: April/04/2013 at 05:31
Gil, Mike might of been kidding about the pencil eraser and then again he might not.... Shocked
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kickboxer Quote  Post ReplyReply Direct Link To This Post Posted: April/04/2013 at 05:50
I'm pretty sure he wasn't kidding...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gil P. Quote  Post ReplyReply Direct Link To This Post Posted: April/04/2013 at 15:18
Never doubted him; I know there are some pretty darn incredible shooters out there.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike McDonald Quote  Post ReplyReply Direct Link To This Post Posted: April/04/2013 at 17:40
seriously, here's how I measure mine;
You know how, when you are looking at the bullet holes on light colored paper, there's a black ring around the circumfernece of the hole?
I use a dial caliper and a magnifier and measure from the outside of that black ring, which theoretically is the true diameter of the bullet as it passed through the target, to the outside of what looks to be the farthest hole on the other side of the group.
Then I shift 90 degrees and measure another two holes.
If I've done my part we're measuring a single hole, looking at the outside of the radii of the group and measuring for example, east/west, then north/south.   I take the largest measurement and subtract bullet diameter for group size.
I then measure group center to the center of the target, which is the aiming point.  That's the true group measure for me;  did I actually put the pointy thingies where I was aiming?
 
For example, here's a test group I fired prone/cold bore when testing the XOTIC prototype for Chris;
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike McDonald Quote  Post ReplyReply Direct Link To This Post Posted: April/04/2013 at 17:42
Sorry, 'puter locked up.
Anyway, you can see it's a decent group with factory ammo, 1 flyer but it happens.
It's also about .35" away from target center, whcih was the aim point, so for me, that's a 0.345 inch group.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote budperm Quote  Post ReplyReply Direct Link To This Post Posted: April/04/2013 at 17:53
Originally posted by Mike McDonald Mike McDonald wrote:

Sorry, 'puter locked up.
Anyway, you can see it's a decent group with factory ammo, 1 flyer but it happens.
It's also about .35" away from target center, whcih was the aim point, so for me, that's a 0.345 inch group.
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sparky Quote  Post ReplyReply Direct Link To This Post Posted: April/04/2013 at 17:56
Very nice! 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kickboxer Quote  Post ReplyReply Direct Link To This Post Posted: April/04/2013 at 18:29
Originally posted by budperm budperm wrote:

Originally posted by Mike McDonald Mike McDonald wrote:

Sorry, 'puter locked up.
Anyway, you can see it's a decent group with factory ammo, 1 flyer but it happens.
It's also about .35" away from target center, whcih was the aim point, so for me, that's a 0.345 inch group.
 
FLyer!?!?!? Shocked  where?

Lower right of the group...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kickboxer Quote  Post ReplyReply Direct Link To This Post Posted: April/04/2013 at 18:34
What he didn't tell you is that one was with his eyes closed...


Mike, that is some outstanding shooting, Sir... just outstanding...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote budperm Quote  Post ReplyReply Direct Link To This Post Posted: April/04/2013 at 19:44
but he said he was having an 'off day'
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Urimaginaryfrnd Quote  Post ReplyReply Direct Link To This Post Posted: April/04/2013 at 19:46
Yep.   Mike has forgotten more than most people will ever know about shooting.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kickboxer Quote  Post ReplyReply Direct Link To This Post Posted: April/04/2013 at 19:49
and STILL knows more...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote robbie Quote  Post ReplyReply Direct Link To This Post Posted: April/04/2013 at 22:19
I walk up to the target, take a look, and say: "hmmm, thats about an inch" or "half inch," or whatever it looks to reasonably be.......
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8shots Quote  Post ReplyReply Direct Link To This Post Posted: April/10/2013 at 09:16
If I do a three round or five round grouping I use the same method... I count three or five holes and call it could. If I find one or two holes short on the target I know my grouping can be tightened up a wee bit.
 
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