Sighting in a short barrel

Discussion in 'Ruger Rifle Forum' started by RHarrison, Nov 6, 2013.

  1. RHarrison

    RHarrison New Member

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    Hi everyone. I just bought a Ruger American .308 youth model. It has an 18 inch barrel. I am having a difficult time sighting it in. I have had so many people tell me different things that I am a bit overwhelmed. First off, I am shooting the Hornady 150gr SST rounds. I decided to get it on paper at 25 yards and had it in the bulls eye. I backed off to 100 yards and wow....6 inches high. I slowly adjusted the scope and got a decent grouping about 2 inches high. But, when I took it back to 25 yards it was still bulls eye. I have tried looking at the trajectory on the shells but cant find one for this gun with the short barrel. Im just looking for some pointers before I go thru another box of ammo. Thanks bunches, Rebecca
     
  2. lucznik

    lucznik New Member

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    Perhaps I'm not understanding your dilemma...

    If you are shooting where you want to at 100 yards and are also on target at 25, what exactly is the problem?


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  3. RHarrison

    RHarrison New Member

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    I guess Im just worried where I will hit at different yardages. When I hunt, some of my shots are at 25, and others are at 300 yards. There are only 100 yard ranges around where I live. I think mostly I would like to know where (yardage wise) to zero it in at and have some trajectory for this short barrel so I have an idea where I will hit at 300 yards. So far it doesnt seem to be close to the trajectory for a regular size .308 or for the box of ammo I am using. I was told if it was a an inch or so low at 25 yards it would be dead on at 100....well 6 inches high is not my idea of dead on....I want to be confident of a clean kill when I take this out in 2 weeks.
     
  4. Pancho_Villa

    Pancho_Villa Well-Known Member

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    Yep, I see no problem there.:D

    Seriously,

    Your barrel ain't that much shorte than a 20 or 22 inch to make alot of difference.

    Also your zero is right as is. Remember when ya come down 4 inches at 100 yards, you are barely moving an inch at 25 yds. It takes TWICE as many clicks per inch on the scope, sometimes more, to get it to move much at 25 yds. So, if ya moved 4" at 100, the most you could have moved at 25 in an inch, if that. It will still be on zero.

    I have experienced that with the bigger bore rifles. Varies some with the lighter calibers and different bullet weights of course.

    So your 2" high zero at 100 yds should be an inch or so lower at 200 and just about right on at 300.
     
  5. lucznik

    lucznik New Member

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    It's hard to give definitive answers without knowing more about your specific load but, as an example:

    My Ruger Compact Rifle (16.5" barrel) firing a 154 gr. Hornady Interbond (or SST) on top of 40.0 gr. of IMR 4895 that departs the barrel at 2660 fps gives a trajectory that looks like this:
    25 yds - 0.17" high
    100 yds - 3.26" high
    125 yds - 3.63" high (this is the peak of its flight)
    200 yds - 2.57" high
    250 yds - 0
    300 yds - 4.16" low
    400 yds - 17.6" low
    450 yds - 27.07" low

    As you can see, the 25 yd and 250 yd marks are where the bullet is crossing the line of sight on its way up and then back down. This setup allows me a "point blank range" of right at 300 yards.

    Your .308 should be easily set up for something similar. Actually, from what you've posted, it sounds like you're almost there already.



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    Last edited: Nov 7, 2013
  6. lucznik

    lucznik New Member

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    Oh, one other thing.

    Other than some small loss of velocity (and when I say small I mean really small; my 16.5" barreled Compact rifle consistently losses only 3-4% of the velocity posted in reloading manuals - despite being 25% shorter than the "standard" 22" barrel) the length of your barrel has no real bearing on your bullets trajectory.


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