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Old 01-03-2011, 08:19 PM
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group measuring ?



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seems from serching here theres so many ways, it a little confuseing, i was curious, where i work at theres usaly little metal slugs thats been punched out of stuff, so, if i had say a 1/4" slug,that i carried to the range with me, and that barely covered a shot group from a 22, would that be considered a quarter inch group ? i was just thinking of mabe a easy way to check groups in general by picking up a few of these slugs to take with me of various sizes, thanks........
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Old 01-03-2011, 08:44 PM
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On Target calculator

Here is what I use, I've been VERY happy with it, and it's FREE:

http://www.ontargetcalc.com

Of course, it does require that you have a scanner or digital camera. Other than that, the only downside is it eliminates excuses and 'exageration error.'

Super easy to use and gives you a record of how your shooting improves (hopefully) over time.
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Old 01-03-2011, 08:56 PM
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Quote:
Originally Posted by Ramius View Post
Here is what I use, I've been VERY happy with it, and it's FREE:

http://www.ontargetcalc.com

Of course, it does require that you have a scanner or digital camera. Other than that, the only downside is it eliminates excuses and 'exageration error.'

Super easy to use and gives you a record of how your shooting improves (hopefully) over time.
I'm hoping for that IPhone app variation!

Thanks for the link!
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Old 01-03-2011, 09:17 PM
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Originally Posted by cbnutt View Post
if i had say a 1/4" slug,that i carried to the range with me, and that barely covered a shot group from a 22, would that be considered a quarter inch group ?
Nope. It would be much less than a 1/4" group. Here's the deal. Let's say you put three bullets through the exact same hole.... literally one right on top of the other. If you use your slug to measure the group you might say you had a 1/4" group. If you measured the size of the hole and called that the group it would be, maybe, 0.22", or slightly less than a 1/4" group. But... you knew there was a but... when we say 1/4" group we mean the two bullets that are furthest apart are 1/4" apart. That's not the case here, is it? You put those bullets right on top of each other. They weren't 1/4" apart, eh?

So, instead, you should measure between the centers of the two holes that are furthest apart. If they stack up right on top of each other, you can't measure that way, eh? Instead, you measure the widest part of the group (include the smudge marks). Now you have to subtract out half the width of the bullet on the left (to get to the center of that bullet) and subtract out half the width of the bullet on the right (to get to the center of that one). What you end up with, after all the subtracting, is the measure between the centers of the two bullets that are furthest apart, and that is the width of your group.

Of course, you've already figured out that instead of subtracting a half-bullet width here and another half-bullet width there, you can just measure the whole group then subtract the width of one hole bullet and get the same result.
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Old 01-03-2011, 09:23 PM
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Originally Posted by cbnutt View Post
if i had say a 1/4" slug,that i carried to the range with me, and that barely covered a shot group from a 22, would that be considered a quarter inch group ?
Not exactly. You have to subtract the diameter of the bullet to get the size of the group if you measure outside to outside. Groups are technically measured from center to center. This means for a 1/4" group, you would need a slug that was 1/4" + the .22 diameter. Now, the diameter of a .22 can vary from bullet to bullet, and from different types of target paper. Measure a few of your single holes to get an average diameter. Then add that to the 1/4" slug, and the 3/8" slug, and the 1/2" slug, and so on.

Edit: Sophia, I should have known you were waiting to pounce.

Last edited by OKShooter; 01-03-2011 at 09:25 PM.
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Old 01-03-2011, 09:30 PM
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Edit: Sophia, I should have known you were waiting to pounce.
... with mouse hovering over the ol' submit post button.
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Old 01-03-2011, 10:15 PM
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Use these if you want a quick and dirty way to measure...



I bought the 6 inch model to use in reloading and general shop stuff. They come to the range with me and I measure groups to help decide what load works best or shooting my Brno to measure what ammo shoots best. Measuring to determine my proficiency is, well....a lost cause. But these 4 inch will work well, they are $16.00 at http://www.harborfreight.com/4-inch-...per-47256.html

These are in tenths, but there also some that measure in fractions (I have one of those for my wood working shop). Cheap and they work well.


Description of Cen-Tech 47256

This 4" digital caliper lets you take inside, outside, depth and step measurements with an accuracy of 0.001" (0.03mm). Measurements are easily read on the caliper's digital LCD display, and the on/off switch has automatic shut-off to preserve battery life. Powered by one 1.5V button cell battery (two button batteries are included).

Last edited by Furnclif; 01-03-2011 at 10:18 PM.
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Old 01-03-2011, 10:27 PM
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Here ya go CB...

(visual aid for measuring groups)


That ought to be pretty self-explanatory As Sophia said, the groups get measured outside to outside, then subtract the average diameter of one bullet to get the center-to-center value. Do something like this and save the results, then after a couple of months do it again and see if there is (hopefully) any improvement.



PS: For quick estimates while at the range, I just use a good 'ol dime. The smaller the group is compared to the dime, the happier I am !!

Last edited by COW 54; 01-03-2011 at 10:40 PM.
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Old 01-03-2011, 11:32 PM
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ok i ( think ) i see how you guys are doing it, if you shoot 5 shots for example, and the distance is 1/2" from edge to farthest edge, .500 minus .220 = a .280 group asumming the hole was .22 of course, i think what ive usaly roughy done in the past was measure the distance from the 2 that are farthest apart center to center, if that disatance was 1/4", then i always said i had a 1/4" group,of course that was just roughly guessing where the center of the hole was.

Last edited by cbnutt; 01-03-2011 at 11:37 PM.
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Old 01-03-2011, 11:38 PM
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Originally Posted by cbnutt View Post
ok i ( think ) i see how you guys are doing it...
Yep; that's it. Subtracting .22" will work for a quick approximation but to get it down to the gnat you should measure a bullet hole from somewhere on the same target. Different paper will create different sized holes, so it's probably not going to be exactly the .22" of the bullet.

Eyeballing the center-to-center measure works too, but when your groups start to shrink down you might find it hard to pick out where the centers of the holes are since they will be overlapping.
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Old 01-04-2011, 12:39 AM
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Originally Posted by Ramius View Post

Of course, it does require that you have a scanner or digital camera. Other than that, the only downside is it eliminates excuses and 'exageration error.'
So having software that doesn't work on the Apple computers is NOT a downside ?

That's why REAL benchresters use one of these…



.

Last edited by deadwooddick; 01-04-2011 at 12:46 AM.
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Old 01-04-2011, 12:50 AM
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Originally Posted by COW 54 View Post
Here ya go CB...

(visual aid for measuring groups)


That ought to be pretty self-explanatory As Sophia said, the groups get measured outside to outside, then subtract the average diameter of one bullet to get the center-to-center value. Do something like this and save the results, then after a couple of months do it again and see if there is (hopefully) any improvement.



PS: For quick estimates while at the range, I just use a good 'ol dime. The smaller the group is compared to the dime, the happier I am !!
That's some good groups. I looked all over but can't find any of that ammo locally to try. was that 25 or 50yds.
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Old 01-04-2011, 11:18 AM
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Geeez, I hope it's 25 yds., otherwise that would make me sad. 4 groups in a row that great, 2 better than I've ever done, at 50 yds. would be incredible.
I'm wondering where he gets the targets, Wal-Mart or grocery. Use them first, or buy them just for shooting?
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Old 01-04-2011, 10:15 PM
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Geeez, I hope it's 25 yds., otherwise that would make me sad. 4 groups in a row that great, 2 better than I've ever done, at 50 yds. would be incredible.
I'm wondering where he gets the targets, Wal-Mart or grocery. Use them first, or buy them just for shooting?
LOL!!!

Those are custom made hybrid targets! The sticky dots came from Wallys, as did the surprising Winchester 333's. The plates,...er ah.. I mean circular target holders came from the local Fred Meyer store (aka Kroegers in some parts of the country) ..and they were NEW, eh... sheesh!!!

They're 4-round groups done for the SSBA cheap-ammo challenge a little while back.. (25 yards from a makeshift front rest and sandbags in back with my Special)

With better ammo (Fed 711b), we were doing sub 1/8" groups with a best group of the day at 0.071 for 5 shots @ 25y.

Still trying to find out what this wonderful rifle can do!

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