100 Yard Range

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by phillietimothy, May 27, 2011.

  1. phillietimothy

    phillietimothy Well-Known Member

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    Hello gentleman. Happy Memorial Day weekend. Thank all of you who have served past and present. I have a weird question. If you are limited to a 100 yard range, with your 100 yard zero set; can you adjust your scope for various ranges and see how high it hits at 100 as a validation tool? For instance, if my ballistic chart tells me that a .223 drops 13" at 300 yards; can I dial 4 minutes, shoot and observe how high it is at 100 and assume I will be on at 300? Thanks.

    Tim
     
  2. craigf

    craigf Well-Known Member

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    Tim, the key is knowing your ballistic chart and your loads well. If you look at the chart and use 300yds as your zero, then look at your MOA at 100yds. ie. 223, 55grn vmax, with a 200yd zero, +1.4" at 100yds, -7.0" at 300yds. But like I said it all depends on bullet grains, powder, powder grns, ect. There are plenty of variables.
     

  3. RockZ

    RockZ Well-Known Member

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    Sorry but the only way to validate is to shoot at the range you want to validate.
    What you are validating is your scope and that the point of impact coincides with the changes you dial in.
     
  4. Mikecr

    Mikecr Well-Known Member

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    +1 RockZ
    You wouldn't be validating your ballistic chart, or bore axis relationships to scope angle.
    Just fiddlin with the scope, which isn't a bad thing to do, but it wouldn't be like actually shooting 300.
     
  5. SBruce

    SBruce Well-Known Member

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    Another +1

    IMO, shooting at 100 is good for evaluating scope adjustments, doing "box" tests and other things to ensure your scope is tracking correctly and accurately. It's also good to get centered up on paper before going out to 200 or 300 for load development. Long ago, I did load development at 100 and then went out to 300 or 400 just to find that the 1/2 minute groups at 100 weren't any where near 1/2 minute at the further distances. In contrast, I've also seen some 3/4 to 1 moa rifles at 100 shoot consistantly 1/2 moa or less at 400...........Dont know why this happens, but I've seen it.

    I've often times seen a different poi at 300 or 400 yds than the charts said with a 100 yd zero. If we're shooting an extremely tight one hole group at 100 (read 1/4 moa or less) then perhaps we will be very close at 300, because the exact poi at 100 is quite easy to tell.

    There are just a few things we need to know exactly in order to dial "dead on" at 300/400 from a 100 yd zero using a ballistic chart. One is the exact height of the scope above the bore, next is the real true velocity of the round, and third is the exact poi at exactly X distance (100 yds) from the muzzle.

    Not trying to discourage you from trying this, there is nothing wrong with giving it a shot, but far too many times I've put in my poi at 100 and got a computer generated 300 yd dope; only to find when actually shooting 300, the numbers didnt' jive......close enough to be on paper of course, but off by 2 or 3 inches from expected. Seen this too many times to have much faith in the status quo 100 yd zero.
     
    Last edited: May 28, 2011