more newbie scope questions

Discussion in 'The Basics, Starting Out' started by regularjoe, Jul 26, 2011.

  1. regularjoe

    regularjoe Well-Known Member

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    Hi Guys, I could use some help with my new set-up.
    I am new to long range shooting and am experiencing "lack-of-experience" issues.
    I am shooting a 300WSM HS Precision which is new. I topped it with a Nightforce NXS 5.5-22 scope on a 20 moa NF base.

    I dialed in the scope to shoot zero at 100 yds... nice 3/4 inch groups with Winchester supreme 180 gr. e-tips, shooting off a back-pack on a four wheeler for a rest. I decided to give a long range shot a try.... backed up to 450 yds, using a ballistic FTE calculator on my iphone it showed a bullet drop of -33 inches. So, I dialed my scope up 28 clicks or 7 MOA.. I torched off six rounds and got a 8 inch group that had a POI eight inches high....... What did I do wrong besides NOT following the well written article on setting up a new outfit found on this site? All comments are welcome including the smart-alec type....... Thank you


    For clarification, I am not concerned about the grouping, but rather why the group at 450 yards was high by so much, I have never used a scope with tactical turrets and am concerned since I got a decent group but too high POI I did something wrong??
     
  2. KRP

    KRP Well-Known Member

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    Dec 25, 2007
    Your math was correct as far as the correction you were given and made(assuming the scope adjusts as advertised).
    Something is most likely wrong with the data you entered as I've always had good luck with JBM's numbers. The old garbage in/garbage out saying is absolutely true.
     

  3. youngbuck

    youngbuck Well-Known Member

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    I'm not familiar with the FTE software. Go through and make sure all your data is correct. I don't think you wouldn't have an issue if everything was correct. I have missed my zero yardage (I zero at 100 and had 200 or 300 in the software) MV and BC are really crucial. It sounds like you may be going off the MV listed on the box of ammo. Have you ran them through a chrono out of your gun? Every gun shoots different speeds, even the same loads.
     
  4. SBruce

    SBruce Well-Known Member

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    Couple of suggestions;

    First, it is a good idea to check the adjustments at exactly 100 yds. From your zero, dial up 20 moa and shoot again. New POI should be really close to 21" high (20.9"). If this checks out, then the scope is adjusting as advertised. To take it a step further, dial back down to zero and shoot again.......bullets should land right on top of your initial group, dial 20 and shoot again.......bullets should land right on top of group #2 (confirms repeatability).
    NightForce should be good, but doesn't hurt to check.

    Second, I've found 100 yd zero's to be quite misleading sometimes. What I mean is that are you Really, Truly dead nuts on zero'd at 100? The scope height is an important thing to know for this, and 3/4 minute groups are tough to tell where your exact zero is too. Something that may help is shoot at 300 yds before moving out to 450. You can then tell the program where you hit at 300 and it should give you an alternative zero distance. Then run the numbers for 450 and see if they come in closer. You might find a few inches difference after doing it this way.

    Third, check your muzzle velocity with a chronograqh. A couple hundred fps faster than you think will mean a sizeable error at 450 yds. A Shooting Chrony is not expensive, and tripods are cheap at Walmart photo section.

    Those are the big 3 that are coming to mind at the moment. A combination of just two of those things could easily give you the 8" higher than expected POI.
    If it were me, I'd also try to tighten that load up some, but 3/4 minute could just be the shooting rest/position. Did you feel comfortable and really steady??

    Oh, one other thing I just thought of........some programs (I've heard) will double compute drops if you input elevation and pressure. Test yours by leaving the elevation at zero and only changing the pressure VS inputing both elevation and pressure...........see if it makes a difference in generated dopes.

    Best Wishes:)
     
    Last edited: Jul 27, 2011
  5. regularjoe

    regularjoe Well-Known Member

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    Great suggestions guys! Just the kind of feedback I was hoping to get. Thank you. I will give these a try and report back.
     
  6. Novus9594

    Novus9594 New Member

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    Did you chronograph your bullets so you know the FPS out of your barrel? Factory specs sometimes assume different barrel lengths than the shooter is using.

    Also, were you shooting at an angle? If you're shooting at an angle and you forgot to put that into your software, your shots will hit high (it's a complex geometry thing to show, but instead of gravity acting straight down like when you shoot level, gravity acts at an angle other than perpendicular when shooting at an angle and therefore causes the bullet to drop LESS than expected).

    What was the weather like on this day as well? Was it substantially hotter than when you zeroed? Was your elevation higher than when you zeroed? What about the barometric pressure... was it lower? At 450 yards, these shouldn't have TOO much effect, but they could be contributors (especially if the differences in temperature and elevation are large).
     
    Last edited: Jul 27, 2011
  7. regularjoe

    regularjoe Well-Known Member

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    Thank you for your thoughts.
    I don't have a chrony yet.... the MV was from the box of ammo. I have a 26" barrel. I don't know what barrel length used by the factory was. I zeroed it before the longer shots (same session) though. The angle was up 7 degrees, no wind, 65 degrees.
    One thing I thought of was barrel heat. Since the gun is new I don't have enough familiarity to gauge what affect that might have. My guess is MV. I need a chrony. I plant to test the scopes "repeatability" this week.

    Thanks again for the input!
     
  8. Novus9594

    Novus9594 New Member

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    Hmmn... barrel heat would widen your grouping (as the barrel changes temperature its harmonics change), but it wouldn't cause you to strike repeatedly higher... just reduce your shot to shot consistancy.

    I'd guess that your ammunition was probably tested on a 24 inch barrel (not sure on that one, just a guess!). The speed difference could possibly account for almost all of that 8 inch difference...

    Another thing to consider... though I've had no experience with this, is that some scopes are wonky. Try adjusting your scope 10 clicks past whatever you need to adjust it, then come BACK those ten clicks (do this after determining that your scope is repeatable). It's an odd sort of phenomenon that for some scopes you have to go too far and come back down (there's an actual term for this, but for the life of me I can't remember it at the moment).