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How do you measure group size??

Discussion in 'Rifle Country' started by Russell13, Apr 12, 2021.

  1. South Prairie Jim

    South Prairie Jim Member

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    I can't speak for short range NBRSA or IBS but Long range has no app scoring just center to center measuring.
     
    Hugger-4641 likes this.
  2. chicharrones

    chicharrones needs more ammo

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    I compare group sizes to coins.

    dimesize.jpg
     
  3. South Prairie Jim

    South Prairie Jim Member

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    What organization uses this method?
     
  4. JDGray

    JDGray Member

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    You see it on westerns as a kid, but you hit a bottle just right, it will fly 15’ in the air! Lol
     
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  5. Walkalong

    Walkalong Moderator Staff Member

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    Center to center. If you are serious, get the attachment for your caliber.
     
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  6. PWC

    PWC Member

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    For competition used to use caliber "plugs" with built in magnifier, to find best/worst edge. Sometimes when it looked like a shot was missed, turn the target over and recounting from the back is more clear.

    Informally, center to center, inside edge to edge, outside edge to edge, group outside edge to opposite side inside edge, all work.

    Remember, statistics don't lie, but they can be manipulated. Just be consistent in method application.
     
    Russell13 likes this.
  7. Offfhand

    Offfhand Member

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    A specialized instrument used in registered short range (100,200,300yds) benchrest competition utilizes magnification lens over appropriate rings. When used correctly measures group sizes to closest.001" Accurate measurement is important in benchrest competitions because the difference between winning and losing may be only a tiny few thousands. Here is the tool I use and pic of scorer at a major tournament using a similar instrument. score1.JPG score2.JPG DSC05191.JPG
     
    Last edited: Apr 15, 2021
  8. doubleh

    doubleh Member

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    Post #19 describes the simplest method. I only compete with myself and that gets it done when I want to measure an especially good group. My MK I eyeball is still fairly well calibrated though and unless it's really a small group I go with that.
     
  9. Jim Watson

    Jim Watson Member

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    My usual approach, as long as it is not the proverbial "one ragged hole".
     
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  10. Archie

    Archie Member

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    Not being concerned with best rest competition, I made up a computer generated group of concentric rings. The rings are one inch diameter then one inch larger to eight inches. Then printed the concentric rings on a transparency. I can take a copy to the range in a folder and use it on the target to give me a quick answer to how big the group.

    Center the rings on the center of the group and slide it around until all the shots are contained in the same ring. (Ignore the aiming point. It has no bearing on group size.) If all the shot holes are within the two inch ring, it is at most a two inch group. For determining which group is 'best' when working up loads, this is quite accurate and much quicker than being concerned about center of each hold and measuring with a micrometer or tape measure.

    Please note this does not remove the need to adjust the sight (iron or glass) to center the group on the target, either paper or biological.
     
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  11. AMraider

    AMraider Member

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    I shoot mainly surplus rifles and surplus ammo. Some mausers but more Mosin Nagants and such. So at 100 yards the groups are either baseball, softball, basketball or garbage can lid size.
     
  12. lysanderxiii

    lysanderxiii Member

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    :scrutiny:

    That doesn't reduce the group's size, just the number that represents it . . .
     
  13. taliv

    taliv Moderator Staff Member

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    It was a joke
     
  14. herrwalther

    herrwalther Member

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    I carry change in my pocket sometimes when I go to the range. Not change like chicharrones though, just normal change. Quarter, nickel, maybe a dime. That is all I really use to compare.
     
  15. Trey Veston

    Trey Veston Member

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    I do center to center. But, I no longer compete in actual matches where such things matter.

    The bigger questions is how many rounds in a group?

    With pistols, I always used a 5-shot group at 25 yards as a standard.

    With rifles, I always did 3-shot groups at 100 yards as a standard. I guess because in my world, rifles are used for hunting, and most hunting barrels lose accuracy after 3 shots due to heating up. Match barrels can maintain consistency for 5 shots, but thinner and lighter hunting barrels are done at 3.

    Hence, 3-shot groups for rifles.
     
  16. Eugen

    Eugen Member

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    I love reading and learning from this thread. I didn't know all the approaches to the question of "how many angels can dance on the head of a pin?". ;)
     
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  17. Picher

    Picher Member

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    I measure center to center of the widest shots...good enough for me, unless the group size is to be published for a match, and I don't shoot matches anymore. Yay!
     
  18. Varminterror

    Varminterror Member

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    This is really the gap for me. I’m shooting 20 calibers any given season, so owning a set of plugs for all don’t make much sense. I can’t eyeball centers, floating in space, nearly as well as I can reference an edge, so without plugs, I simply measure O-O, then subtract the diameter of a hole (example: the holes on the paper I shot last week are .225-.228”, despite the fact a .243” bullet passed through it).
     
  19. barnfrog

    barnfrog Member

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    MOGCL?
     
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  20. AK Hunter

    AK Hunter Member

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    I'm a hunter as long as I can cover all the holes with my fist it's good. A deer heart is about the size of your fist.
     
  21. 71GTO

    71GTO Member

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    Since I seem to always exaggerate my group size anyway (like the size of the fish) I usually just estimate and for some reason always end up being inside of 1 MOA. Lol
     
  22. AMraider

    AMraider Member

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    First time shooting a Sestroryetsk M91 from 1916. Bore is in bad shape and the crown is more like a Blunderbuss. It must have suffered severe steel cleaning rod use. 10 rounds at 100 yards = No hits. 10 rounds at 50 yards = 1 hit.Sidways. 10 rounds at 25 yards at BIG target = MOGCL. : )

    47Ma.jpg Ses1.jpg
     
    chicharrones likes this.
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