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# How do you correctly measure groups ?

#1
01-01-2008, 06:20 AM
 Gold Member Join Date: May 2007 Location: VICTORIA AUSTRALIA Posts: 912
How do you correctly measure groups ?

Just wondering the correct way to measure group sizes. I would imagine it is some calculation with verticle spread, horizontal spread and distance shot at ?

I just shot the group of my life so far- 1.75 " centre to centre of all 3 shots horizontally and .75" verticle spread centre to centre at 700 Meters. What does this equate too ?

Don't really know ?

DUH
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Last edited by Down Under Hunter; 01-01-2008 at 06:28 AM..
#2
01-01-2008, 06:42 AM
 Platinum Member Join Date: Mar 2007 Location: MN Posts: 1,218
Just measure the width of the two outermost holes, avereage them, measure from the outside point to outside point, and then subtract the average width of the holes (the reason for measureing the actual width of the hole is because paper stretches or tears irradically sometimes- a 30 cal bullet may or may not leave a .308 inch hole). Way to go on your group!
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#3
01-01-2008, 07:52 AM
 Silver Member Join Date: Jun 2006 Location: Memphis, TN. Soon to be Casper, WY. Posts: 494
Quote:
 Originally Posted by Down Under Hunter I just shot the group of my life so far- 1.75 " centre to centre of all 3 shots horizontally and .75" verticle spread centre to centre at 700 Meters. What does this equate too ?
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#4
01-02-2008, 10:55 PM
 Platinum Member Join Date: Jul 2004 Location: SW MO Posts: 1,085
Great group!
For all practical purposes, one minute of angle (1 MOA) equals one inch at 100 yds, two inches at 200 yds and so forth. So what stormrider said basically means you shot the equivalent of a 1/4" group at 100 yds--although what you did would actually be harder due to wind drift and velocity differences from shot to shot at that distance. Your vertical dispersion is a better indicator of load precision at long range than horizontal spread due to wind drift, assuming your barrel is free floated and is not excessively hot during shooting.
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#5
01-02-2008, 11:42 PM
 Platinum Member Join Date: Jan 2004 Location: Blackfoot, Idaho Posts: 7,840
You said: I just shot the group of my life so far- 1.75 " centre to centre of all 3 shots horizontally and .75" verticle spread centre to centre at 700 Meters. What does this equate too ?

Measure with calipers from outside edge to outside edge of the carbon mark of the widest shots. Then subtract at least one caliber and maybe fudge just a little. Then round it of DOWN to the nearest 1/100th. That's the group size that you advertise.;)

the sad thing is that if that rifle does it once, "IT" will do it all the time.:o
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#6
01-03-2008, 12:08 AM
 Gold Member Join Date: May 2007 Location: VICTORIA AUSTRALIA Posts: 912
Quote:
 Originally Posted by royinidaho You said: I just shot the group of my life so far- 1.75 " centre to centre of all 3 shots horizontally and .75" verticle spread centre to centre at 700 Meters. What does this equate too ? I reply: Great Shootin' Measure with calipers from outside edge to outside edge of the carbon mark of the widest shots. Then subtract at least one caliber and maybe fudge just a little. Then round it of DOWN to the nearest 1/100th. That's the group size that you advertise.;) the sad thing is that if that rifle does it once, "IT" will do it all the time.:o

Roy,

Just pleasing to know it has the capability, even if I dont ?

I'm going to stick a jewell trigger in it, so hopefully thing can only get better as they say !

Cheers guys !

DUH
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#7
01-03-2008, 12:38 AM
 Platinum Member Join Date: Sep 2004 Location: on the rifle range in Utah Posts: 2,723
The confusion of group measuring may account for why I hear "my gun shoots 1/4" all day long" so many times a week. I think those guys are measuring the paper between the closest two holes!! Either that or every swinging Harry that says that is shooting competitive benchrest aggs every time he goes out and I doubt that very seriously.

The best way to field measure is to do like Roy said. Measure from outside to outside of the hole and subtract the caliber. But that way is still not accurate enough for benchrest measuring. We actually have a tool that attaches to a caliper and works very well and much more accurate.
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