Holdover\holdunder at different increments

Discussion in 'Night Vision/Thermal' started by Jack M, May 10, 2020.

  1. Jack M

    Jack M The Student

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    Hey everyone. I got a question for y'all. I'm running a pulsar xq38 lrf on a DD M4A1 .223. I zeroed it in at 50yds and it's a tack driver. At 20yds it shoots 1" low. At 100yds 1.5" high. At 150yds 3" high. At 200tds 4"high. And at 225yds 6"high. The inches are all estimated, yardages are from the built in range finder. So my question is is it normal to have to holdunder with yardage increase? It's been awhile since using glass and can't remember. Also at each yardage I did 3 shot groups and each group the shots were less than 1\2 inch apart.
    Thanks
    Jack
     
  2. Brian Shaffer

    Brian Shaffer Hog Hunter SUS VENATOR CLUB LoneStarBoars Supporter

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    Sorry, but that is totally messed up. You have bullets impacting in a bizarre pattern, first along a linear scale, then curving downward off the line, and skyrocketing upward at 225. Ballistics don't typically work like that where bullets go down and then back up.
     
  3. Jack M

    Jack M The Student

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    Exactly. It's the exact opposite of what it should be.
     
  4. Jack M

    Jack M The Student

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    Any thoughts on why this is happening?
     
  5. Jack M

    Jack M The Student

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    I will also video it tonight when it cools down so you can see what going on
     
  6. Chopperdrvr

    Chopperdrvr Deep East Tx SUS VENATOR CLUB

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    I don't know if its just me, but you guys don't seem to be saying the same thing. If he is zeroed at 50 yds and 1" low at 20 yds, that is perfectly normal. The bullet starts out lower than the line of sight until it intercepts the line of sight at the zeroed distance and continues to climb until it reaches the apex of the bullets path which in this case seems to be somewhere beyond 225 yds. The bullet didn't go down then back up, it started down and continued to climb. Rather consistently.
     
  7. Brian Shaffer

    Brian Shaffer Hog Hunter SUS VENATOR CLUB LoneStarBoars Supporter

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    Dave, you have to plot it out. He has a different amounts of rise of run that don't follow a normal ballistic curve.

    For example,
    He gets 1.5" of rise over 50 yards run from 50-100 yards.
    He gets 1.5" of rise over 50 yards of run from 100-150 yards....this looks more linear than it should look, but maybe that is a fluke.
    He gets 1" of rise over 50 yards of run from 150-200 yards, ...this looks like it is leveling off as you would expect,
    but gets 2" of rise over 25 yards of from 200-225 yards. ... so the bullet is now heading up at a previously unprecedented level.

    Bullets don't fly like that.
     
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  8. Rookie

    Rookie LSB Member

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    50 yard zero should be close to zero at 200ish and dropping from there...
     
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  9. Ratdog68

    Ratdog68 LSB Official Story Teller LSB TURKEY BUZZARD PRESERVATION SOCIETY SUS VENATOR CLUB LoneStarBoars Supporter

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    Kind of what I was thinking.
     
  10. Jack M

    Jack M The Student

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    I haven't gotten around to making a video yet to show you guys. Was about to but then walked up on a hog. Will try for tomorrow. Thanks for all the replies.
     
  11. pruhdlr

    pruhdlr Cantonment,Fla. SUS VENATOR CLUB

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    You have the bullets path which is a arc. Then the sight,scope,thermal,NV,it does not matter,line of sight which is like a laser.
    The bullets arc crosses the line of sight twice in it's normal travel to the target if it is somewhat distant.
    The ( my) basic thumb rule for a 223/5.56 is - - -> "on at 50 . . on at 150". This is pretty much true in it's simplest form.
    Most all my guns,even my large bore guns like 45-70,458Lott,500S&W,etc,are sighted in for " the first" zero at 50yds. Then I run the figures thru the JBM CALCULATIONS (TRAJECTORY) site to fine tune everything.
    Been doing this for years. Believe the figures it spits out. And remember - - -> INFO IN <---> INFO OUT. --- pruhdlr
     
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  12. J BAR K

    J BAR K Just trying to make a day. SUS VENATOR CLUB LoneStarBoars Supporter

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    Perhaps the Warren Commission should be consulted... they have experience with bullets and unusual trajectories??
     
  13. Jack M

    Jack M The Student

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    Great info thank you.
     
  14. Chopperdrvr

    Chopperdrvr Deep East Tx SUS VENATOR CLUB

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    You are right, I was just looking at it as a whole trajectory and not paying too much attention to the intermediate impacts were. The height of the optic above the bore will make a big difference in where that second “zero” point would be and I was thinking that his combination just hadn’t reached the apex of the arc yet. I guess that would still make it a pretty flat shooting round.
     
  15. Jack M

    Jack M The Student

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    I currently only have one zero point and that is at 50yds. Do I need a second zero point for a thermal?
     
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  16. Chopperdrvr

    Chopperdrvr Deep East Tx SUS VENATOR CLUB

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    No, but it is helpful to know where your bullets trajectory will cross your point of aim on its way to the earth. This point will be the second point of zero. You should actually see that before 225 yds which has caused this thread to get so involved since your point of impact was still well above the line of sight.
     
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  17. Ratdog68

    Ratdog68 LSB Official Story Teller LSB TURKEY BUZZARD PRESERVATION SOCIETY SUS VENATOR CLUB LoneStarBoars Supporter

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    This is what is being discussed Jack.

    [​IMG]
     
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  18. Jack M

    Jack M The Student

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  19. Jack M

    Jack M The Student

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    Ok I see now what you're saying. Thank you
     
  20. Jack M

    Jack M The Student

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    Ok so I finally got around to taking a picture of my issue. The shots in blue are at 50yds and the red at 100yds. Shooting a DD M4A1 in .223 with a 1:8 twist. Ammo is tulammo 75gr HP. Thermal is a pulsar xq38LRF with latest firmware. 20200522_185721.jpg
     

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