MOA at 400 but can't get on target at 650?

Discussion in 'Long Range Hunting & Shooting' started by Tommy1984, Sep 19, 2019.


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  1. Joefrazell

    Joefrazell Well-Known Member

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    If your actually shooting 3" groups at 300 yards then I'd say it's not a load issue. Not at 650. Did something change in your shooting position? Also, check your parallax. Last, when it throws huge groups like that go back to 300 and shoot. See how it performs. There's no way an accubond should be falling through transonic at 650. It should be plenty good and stable
     
    powderBurnz likes this.
  2. John Klingenberg

    John Klingenberg Well-Known Member

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  3. John Klingenberg

    John Klingenberg Well-Known Member

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    If that pic you posted is your 100 yd you have to realize also that little bit off center translates to that group being 6x larger and about at that upper right diamond. 100 yd zeros have to be absolutely centered
     
  4. rgmeddn

    rgmeddn Member

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    Of all the suggested causes, the ONE that seems most likely is jerking your head up to see the impact.
    Please let everybody know how it ends!
     
  5. GonzoK34

    GonzoK34 Well-Known Member

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    Carbon wrapped barrels are fine for hunting when one or two shots are taken. But remember you have a thin barrel under the carbon fiber. My son bought a Gunwerks Rifle carbon barrel in 6.5 x 284 Norma it's a great rifle. $$$$$ He "LEARNED" the hard way that you can't shoot long strings of fire. When the rifle was new he shot 20 rounds with cleaning after each 3 shot string at 100 yards. Good to go. Then he went out to 300 yards shooting 5 round groups, nice. 600 yards 5 rounds 10"+. 700 yards rounds spread out 20",???? My observation he was shooting too many shots without a cool down. I took the rifle apart removing the scope and base, cleaned it removing the carbon and copper. Remounted the base, rings and scope. Took it out to the desert zero'd at 50 yards with 2 shots. Fired 1 rd at 100. Moved to 200- 3/4", 300 - 1.5", 400 - 2" , all with 2 shots fired at each distance. Cleaned the rifle. The next weekend we confirmed data to 1400 yards with great results. All shots were in groups of 2 with a couple of minutes cool down between shots.
    Again, it's a super thin barrel we have witnessed barrel flip if the shooter shoots a rapid fire string of 5 -10 rds. Accuracy goes out the door.
    Key: Firm grip on the stock, snug against shoulder, consistent spot weld, sight picture, quarter the target, breathe, squeeze the trigger, follow through, maintain sight picture through recoil, sights/crosshair should settle on point of aim/point of impact.
    Done correctly your shots should impact in a nice tight group.
     
    lyle2231 and Zymurgist like this.
  6. milo-2

    milo-2 Well-Known Member

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    For what the op tried to accomplish that day, it would matter in the least if he had a solid zero on his scope. He could not spot his impacts.
    https://www.longrangehunting.com/th...unworks-1-760-yard-steel-target-range.137397/
    I've cleaned this range a dozen times with a non zeroed scope on new barrel doing load dev, or a new scope. You just have to know where the turret is. I don't even boresight a new system today, just fire at 500 yards, get on a 10" plate, do the math and bring it back to 100 to set the zero.
    The op has been sent on a wild goose chase, I just hope his head doesn't explode. This stuff is not complicated.
     
    Chase723 likes this.
  7. LazzInc

    LazzInc Official LRH Sponsor

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    Gonzo ,,,, I think you hit the nail on the head ,,, if it is a carbon wrapped barrel those are sometimes only good for 2-3 accurate shots between FULL COOL DOWN or the groups can open up dramatically ,,,,
     
    Zymurgist likes this.
  8. powderBurnz

    powderBurnz Active Member

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    Depends on whos cf barrel it is.
     
  9. Michael Cantor

    Michael Cantor Well-Known Member

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    My guess is your elevation is off. It may be in your dials. Did you make sure your scope shoots an accurate box test? Doesn't matter how expensive the scope or the reputation. Each scope is individual. Check out the scope report on accurateshooter.com. Gunwerks may tell you what your elevation "should" be, assuming your scope tracks accurately.
    ALSO, are you using a bubble level and is your vertical crosshair perfectly in line with the bore when it is plumb?
    You may have componding errors, but my guess is your elevation correction is off. See if you can shoot a group at 650.
    At 650 I think your velocity should be around 1700 -1800 fps so you are well above supersonic.
     
  10. Michael Cantor

    Michael Cantor Well-Known Member

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    I may have missed the part about long strings of fire.... a Carbon wrapped barrel? Is meant for lightweight carrying and 1 or 2 or 3 shots. Not strings of target shooting... not with a 300 Mag. Maybe a 204 or 223 could take 8 or 10 rounds before heating up significantly. Even a sendero weight barrel is minimal for 3-5 shot strings for a 300 mag.
    Try again.
     
    Zymurgist likes this.
  11. Chase723

    Chase723 Well-Known Member

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    Couple things...probably already answered in the thread but here’s my .02 to join the lot.

    Things change pretty drastically between 400 and 600 yards. You go from short range to medium range and environmental factors and shooter error become increasingly more important.

    1) the group you posted is 1/2 MOA high and right at 100 yards. At 600, even if everything is perfect, you’re going to be off center by at least 3 inches.

    2) if there was even a 3mph wind, which is barely perceptible, with that bullet at that distance you’ll be off by ~0.3 mils, or ~1 MOA. So now w/ the above you’re 9 inches off target before you even start.

    3) you’re ammunition likely has an ES > 30, probably like 50-80. If that’s the case, at that distance, then you’ll have an additional 3 inches or so of random dispersion. I.e. a ~1/2 MOA of precision out the window. So now you’re at least 12 inches off at 600. That 1/2 MOA at 100 is now 2 MOA at 600. Since if we make the assumption that you’re a perfect shooter, and your load opened up by 1/2 MOA from 100-400 yards, that’s actually quite a bit. If you’re ES was less than 30 than it should be ~ 3/4”.

    Common Shooter errors

    4) Paralax is off/head position behind the scope varies between shots. At 600 that can easily be 1/2- 1 MOA different. So now you’re 3 MOA at 600.

    5) Inconsistent trigger pull/flinching. Add another 1/2-1 MOA. Now you’re 4 MOA at 600.
     
  12. brentc

    brentc Well-Known Member

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    Parallax!!
     
  13. desertcrr1

    desertcrr1 Member

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    There are all kinds of things that begin to affect accuracy at about 650 yards, but you have most of them covered. One of them not discussed so far is the accuracy of ranging. If you look at the drop vs. range profile of almost any cartridge, this is the range at which the bullet is really starting to drop. If the range estimate is off just by a few feet a bullet can impact in front or behind a target that's not really tall from just a small variation in muzzle velocity with everything else perfect - which it never is. The nice even number of "650" when ranging to a rock might well cause a miss if it were 648 or 652. I don't know what the "ballistic calculator" in your RF uses but I would also encourage checking it against Hornady's 4DOF just to see. Also, chronograph at least 10 rounds, compute a SD and a 5 or 10% max and min V0. Plug these two extremes into 4dof and get the poi elevation extremes at 650 and compare with the height of the rock. This will tell you the precision needed to hit that rock.
     
    Chase723 likes this.
  14. Sniper97

    Sniper97 Well-Known Member

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    Could be the scope too!