Correct Way to Measure 3 Shot Group

Discussion in 'Long Range Hunting & Shooting' started by jeffwhip, Sep 14, 2011.

  1. jeffwhip

    jeffwhip Well-Known Member

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    I'll chalk this up to yet another pretty basic question I'd like to know. What is the correct way to measure a 3 shot group? Do I measure from the outside edge of one shot to the furthest outside edge of another shot and then subtract the bullet diameter? In the case of a 7MM I would subtract .284? Thanks in advance!
     
  2. 6.5x284tony

    6.5x284tony Well-Known Member

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    Yes, you are correct! I went round and round with a friend about this once. He was shooting a .223 and I was shooting a .300 ultra mag. He thought that since the outside measurement of his group was smaller, he had the better group, that is until I explained the proper way to measure the group.

    Tony.
     

  3. jeffwhip

    jeffwhip Well-Known Member

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    Thanks Tony!
     
  4. sambo3006

    sambo3006 Well-Known Member

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    Depending on the surface you are shooting at the apparent hole the bullet leaves may be slightly smaller than the actual bullet diameter due to a less than clean cut of the surface. If you look closely you can see the real outer edges of the impact. Measuring it properly can add a tenth of an inch to the measurement which is bad for the ego but good for precision.:D
     
  5. scap99

    scap99 Member

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    I've found that using a program like OnTarget takes the guess work out of it.

    Just take a pic of the target if you can't put it on a scanner....
     
  6. silvertip-co

    silvertip-co Well-Known Member

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    You may measure it however but please carry it out to at least as many digits as Pi as many do on here.

    ex. a three+ inch group on these forums is measured as such: 3.1416159287

    Now where did I put my barrel tape.
     
  7. WildRose

    WildRose Well-Known Member

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    I don't bother with the subtraction. Just measure the maximum outside spread but then I'm not worried about impressing anyone with my size... .gun)

    The shot that really matters is the first cold bore shot anyhow but I like to use two rapid follow up shots.

    In the field the first is the most critical and you'll rarely get an opportunity for more than two follow up shots.

    If you can maintain sub MOA accuracy with the first cold bore shot always being repeatable you have a reliable weapon to hunt with.

    Yep it's cool to see just how tight you can get a 3-5 shot group letting the weapon cool down in between etc but I'm a hunter and predator controller so I approach it differently than a target shooter.
     
  8. WildRose

    WildRose Well-Known Member

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    How about a micrometer and a slide rule? I probably have a couple of extras... HA!

    They are well cared for and haven't been used since at least 1981.