horizontal stringing

Discussion in 'Reloading' started by bullfrog, May 7, 2015.


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  1. bullfrog

    bullfrog Well-Known Member

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    I have a Model 70 6xc completely built by GA Precision (trued action, bedded, with muzzle brake) with a 1:7.5 twist Bartlein barrel. I have been unable to find a load with small extreme spreads and consistent accuracy using RL17, H4350, and H4831SC with any bullet or primer so I tried faster powders. IMR 8208XBR and Varget both had very good extreme spreads of around 12fps with 107 SMK's and 105 Berger Hybrids. When developing these loads it was very windy and I had horizontal stringing which I attributed to the gusty wind. I shot the best loads again on a calm day and still had horizontal stringing. The groups averaged about 1/4" or slightly less vertical with 1/2" to 1" horizontal. I loaded up some H4350 with 107 SMK's just to see if they were also horizontal stringing (I have shot this load before with mediocre accuracy and extreme spreads larger than I like but it was somewhat proven). It was not a great group (.59" for 5 shots) and the ES was 38fps but this load did not have horizontal stringing. I checked the rifle over. Barrel is free floated very well, magazine box is not binding, removed scope and checked bases, checked scope rings, and checked torque on action screws. Everything on the rifle checked out.

    Varget and IMR 8208 XBR have been the only powders that have had consistent velocities for this rifle. What would cause these powders to string horizontal? Is there anything you guys think I should try?

    I've put over 400 rounds thru this rifle trying to find a load with good accuracy and consistent velocities and I am getting FRUSTRATED.
     
  2. eshorebwhntr

    eshorebwhntr Well-Known Member

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    Apr 11, 2009
    Pretty odd...

    I guess you feel you've done enough testing to repeat the case that the faster powders always string and the slower powders always don't?

    The first thing I would do is shoot the two different combo's the same day as close to the same conditions as possible if you haven't already.

    Load 10 that string out (varget or whatever) and 10 that don't (4350 or whatever). Use brass that is all in the same condition. Same headstamp, #x fired, etc.

    Shoot 2 separate 5 shot groups of each. Off bags or rest instead of a bipod if that was a variable during previous testing.

    Maybe have a buddy you trust as a good trigger man get behind the gun.

    What range are your verifying your vertical stringing at? I typically verify good (or bad) chrono numbers (ES and SD) on paper at 5-600. You would have to have a seriously bad ES to notice any difference at 100.

    I'm probably not much help here but I've just never heard of a bad powder/bullet combo only stringing horizontal. Usually its an opened up scatter. I have, however, shot along side of a lot of guys that blamed poor mechanics and trigger discipline on coriolis and spin drift at 400-500. I'm not at all blaming you. But when it comes to true, quality, precision rifles, we are usually the least precise part of the puzzle.

    Good luck. I hope you can get it figured out. Nothing is more frustrating than our favorite toys not working right.
     
  3. barefooter56

    barefooter56 Well-Known Member

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    bullfrog,
    Did you have wind flags set out? Or at least a piece of surveyors tape attached to the target backer? That's not much horizontal movement with the VARGET and 8028XBR load testing description. And very good Vertical. Set out some flags and re-test. It may be calm where you are standing but on out?
     
  4. FearNoWind

    FearNoWind Well-Known Member

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    I realize that you're focused on powder as the source of your problem but I have to ask - what are you using as a butt bag (if any) and is your cheek weld consistent? Anything that puts the butt off axis will cause horizontal stringing and it's often difficult to detect slight variations in butt bag placement and cheek weld consistency.
     
  5. bullfrog

    bullfrog Well-Known Member

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    To clarify a little more. I am shooting off a stable bench with a high quality adjustable front rest and rear bag. I have done all my testing of the faster powders at 100 yards and the groups referenced in my first post were all shot at 100 yards on a calm day (no wind to speak of anywhere). I have previously shot the slower powders at long range to make sure what I was seeing at the chronograph (Oehler 35P) was translating out to 1000 and it was. I had about a foot of vertical at 1000. I was not happy with this and have been trying to find a load with small extreme velocity spreads and did not have any success until trying 8208XBR and Varget. I have shot 350 rounds of load development with H4350, H4831SC, and RL17 without seeing anything that was stringing horizontal. I shot 50 rounds with the faster powders and the groups were clearly horizontal the entire time. It could be the fault of the shooter (me) but I don't think it is. I double check parallax every time out and take great care with my technique. My other rifles are shooting fine.

    All shooting was done with the same brass (brand, lot, and X's fired), same lot of primers, same lot of bullets, same amount of neck tension, and all shot on the same day with the same setup, temp, conditions, etc. I know a lot of guys like to shoot farther than 100 yards but I don't want to waste the time and money shooting groups at long range when I know the load is not shooting as good as I want at 100.

    I guess I was hoping someone had seen this before and might be able to point me in a direction to take.
     
  6. barefooter56

    barefooter56 Well-Known Member

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    bullfrog,
    Concentrate on lowering the Standard Deviation (SD) to get rid of the vertical. 10 or below should be reachable. The lower the SD the lower the vertical spread. You may be there on the horizontal as mentioned before. It doesn't take much for mother nature to move a bullet sideways even at 100 yards! And vertical is way more important at 1000 yards !
     
  7. RockZ

    RockZ Well-Known Member

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    I just did a test the other day shooting from a bipod at 100yds. For the first group I shot 5 rounds with the rear bag ,bipod,rifle set up perfectly as if it were in a bench rest setup and shot with my best form.
    The 5 shot group measured .269"
    For the next group I pulled the rifle hard to my shoulder without carefully aligning the rifle ,bipod and rear bag and shot a 5 shot group.
    It was nearly a perfect horizontal line with all bullets touching...
    I made the horizontal.
     
  8. frankinaustin

    frankinaustin Well-Known Member

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    Oct 2, 2013
    FWIW, I have found that when I spend a good amount of time at the start making sure to set the parallax correctly for the range and zoom, that my groups seem to be better.

    What I do is get the side focus (I know its called a parallax adjustment, but I'm from Texas...) pretty close to what looks focused and then I slightly nod my head up and down and make slight tweaks until the horizontal line of the reticle no longer appears to move up and down with my head nods. When that horiz cross hair stays steady with the horiz line on my target, then I'm "on." However, this is slightly not perfectly in focus for my old hard boiled egg eye balls, that just don't see as good as they once did.
     
  9. paste

    paste Well-Known Member

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    May 17, 2009
    have you tried different bullet seating depths??
     
  10. Dgd6mm

    Dgd6mm Well-Known Member

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    Bingo.... This was not my first thought, it was my second. First is I did not read any mention of a scope level being used, which I know does not mean that you don't have one and using it, just no mention. Second seating depth usually shrinks horizontal stringing.