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Thread: Hornady .308 165gr SST - Trajectory Question

  1. #1

    Hornady .308 165gr SST - Trajectory Question

    Looking at the trajectory on the Hornady website, it says that with a 200 yard zero, it's going to be 1.8 inches high at 100 yards. This may be a stupid question, but how does that translate with a 100 metre zero at 200 metres? 1.8 inches low?


    Hornady Manufacturing Company :: Ammunition :: Rifle :: Choose by Caliber :: 308 Win :: 308 Win 165 gr SST® Superformance®

    Thanks in advance for any help.
    Cheers
    T_T

  2. #2
    TT,

    There are no stupid questions...just dumb answers!

    The bullet will describe an arc or more exactly a parabola. If you think about how the bullet reaches the 200m mark it is because you need to angle the muzzle upwards to describe that flight....at a 100m zero you will have the muzzle lower. Gravity will affect the bullet from the moment it leaves the barrel so by the time it comes to the 200m mark when zero'd at 100m it will be well below 1.8inches....

    Bottom line is you are looking at a 4.5" drop on a 165SST for a 100m zero at 200m!

  3. #3

  4. #4
    2-0-9 , 2" high at 100m 0 at 200m and 9" low at 300m , works there or thereabouts with all common deer type calibres , certainly good enough to get killing hits.
    Right where's those stones , I'll start !

  5. #5
    Quote Originally Posted by Dorsettaff View Post
    TT,


    Bottom line is you are looking at a 4.5" drop on a 165SST for a 100m zero at 200m!
    Mixing units of measure makes this rather confusing. Better to use inches and yards or millimeters and meters.

    Anyway, 4.5 inches seemed rather much to me given that it would be more than a 2 MOA change at short range. I used Hornady's calculator with their publsihed BC (0.447) and muzzle velocity. That predicts an impact 3.5 inches low at 100 yards this of course is 1.75 MOA. When applied to meters where 100M = 109yds and 200m = 218yds the diference will beinfinitesimal.

    http://www.hornady.com/ballistics-re...ics-calculator

  6. #6
    Quote Originally Posted by MARCBO View Post
    Mixing units of measure makes this rather confusing. Better to use inches and yards or millimeters and meters.

    Anyway, 4.5 inches seemed rather much to me given that it would be more than a 2 MOA change at short range. I used Hornady's calculator with their publsihed BC (0.447) and muzzle velocity. That predicts an impact 3.5 inches low at 100 yards this of course is 1.75 MOA. When applied to meters where 100M = 109yds and 200m = 218yds the diference will beinfinitesimal.

    http://www.hornady.com/ballistics-re...ics-calculator
    4.5'' drop at 200m with a 100m zero sounds about spot on to me ?
    Right where's those stones , I'll start !

  7. #7
    Quote Originally Posted by tackb View Post
    4.5'' drop at 200m with a 100m zero sounds about spot on to me ?



    Reminds me of some guys that used to work for that relied on "I think..." I feel..." and "I believe..." No facts could dissaude them.

  8. #8
    Quote Originally Posted by MARCBO View Post


    Reminds me of some guys that used to work for that relied on "I think..." I feel..." and "I believe..." No facts could dissaude them.
    in fact I know it's near enough spot on as I've actually shot these bullets in my 308 at most ranges and the 168 amax plus many other different bullets , would you care to use some of your facts to show me where I'm wrong ? I don't mind imperial or metric or a combination I'm familiar with either ?
    Right where's those stones , I'll start !

  9. #9
    Quote Originally Posted by tackb View Post
    2-0-9 , 2" high at 100m 0 at 200m and 9" low at 300m , works there or thereabouts with all common deer type calibres , certainly good enough to get killing hits.
    Yes, most standard deer cartridges are going to be about about like this. If you think you will be shooting at 300, get the holdover exactly where you want it at 300 ( eyeball, ballistic reticle, Mil Dot, or to the duplex at a certain power), then shoot to find the drops at 200 and 100. It may come out to +2.25 at 100, +0.5 at 200, and -7.0 at 300. The odd 1/4 inch at shorter ranges are easier to ignore than some large and oddball value at 300.

    Edit: English units ( the way I think, yards, inches, MOA, 1/4 inch clicks)
    165-gr .308 bullet at 2,800 fps with a BC = 0.450 approximately
    Drops in inches...
    A hot load (2,900 to 3,000 fps), same sight setting changes 300 to -7.0, 400 to -20.0, 500 to -40.0
    Muzzle 100 yds. 200 yds. 300 yds. 400 yds. 500 yds.
    2800 1.8 0 -7.6 -22.1 -44.7
    Last edited by Southern; 10-12-2014 at 22:25.

  10. #10
    Quote Originally Posted by MARCBO View Post
    Mixing units of measure makes this rather confusing. Better to use inches and yards or millimeters and meters.

    Anyway, 4.5 inches seemed rather much to me given that it would be more than a 2 MOA change at short range. I used Hornady's calculator with their publsihed BC (0.447) and muzzle velocity. That predicts an impact 3.5 inches low at 100 yards this of course is 1.75 MOA. When applied to meters where 100M = 109yds and 200m = 218yds the diference will beinfinitesimal.

    http://www.hornady.com/ballistics-re...ics-calculator
    Mixed units of measurements is very much a fact of life in the UK. All we learnt at school was metric, but as soon as we were finished in school a metre became "about three feet". Officially everything is metric, but in daily life it's a different kettle of fish (or was at least before I emigrated!).

    Thanks for the link to the ballistic calculator. Looking at the data given for a 100 yard zero, it says a 3.5" drop at 200 yards and 7.4" at 250. As such 4.5" at 218 yards sounds very likely indeed.

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