What causes horizontal and vertical strings

Discussion in 'Reloading' started by berger21, May 8, 2011.

  1. berger21

    berger21 Member

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    I've been trying to work up some loads for my Sako A7 300 win mag. This weekend I tried 3 different powders and 3 different bullets and shot 3 shot groups in 9 sets. Temperature was about 60 degrees with a 10 to 15 mph wind moving left to right with the target at 240 yards. I was shooting off a bench with sand bags and rifle butt support.

    I was able to get several decent groups and there were several that strung bullets either vertical or horizontal. After each 3 shot group the rifle was cool to touch. (about 20 minutes between rounds) Here are some of the better rounds and some of the ones I would like help deciding why this happens.

    All shot at 240 yards.

    200 gr. Sierra Game Kings shooting 80 grains of H1000 1 5/8" group
    185 gr. Berger Hunting VLD shooting 73 grains of H1000 1 7/8" group
    185 gr. Berger Hunting VLD shooting 73 grains of 7828 SC 2 1/2" group

    165 gr. Hornady Interlock BC shoot 75 gr. of 7828 5" group with a vertical string
    200 gr. Sierra GK shooting 70 gr. of 7828 6" group strung horizontal.

    Just wondering why I would have a vertical and a similiar horizontal string. I was confident in my shot placement as I am using a 4X12 Leupold Var X II.

    Please let me know what you think.
     
  2. elkaholic

    elkaholic Well-Known Member

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    It could be any number of things but I would try changing the seating depth and see what happens......Rich
     

  3. berger21

    berger21 Member

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    I can only shorten them as I am loading 3.34 and this rifle has a detachable magazine and factory loads are maximum length.
     
  4. elkaholic

    elkaholic Well-Known Member

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    Just re-read your post and noticed the wind. That kind of wind would certainly account for a lot of horizontal at that distance. I think I would first try the same loads shooting in calm conditions.......rich
     
  5. Gene

    Gene Well-Known Member

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    There are many possible causes. One I would suggest is your bench technique. What front and rear rests do you use? Are they level? Does rifle return to exact position after each shot? Are you holding same each shot? Your story is one I used to sing several years ago; until I learned to keep everything repeatable from shot to shot.

    PS - Get books by Tony Boyer or Mike Ratigen for more info on this subject.
     
  6. Jinx-)

    Jinx-) Well-Known Member

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    Sounds like my shooting this weekend, only winds was 5 - 7 at the times changing direction from wsw to wnw to north. At 300 yards I saw a drop about 4" from almost one hole group from warm barrel and at 100 yards there was a jump 1.5" from cold barrel, so I limit my fliers to copper falling caused by excessive speed, basically I was shooting 55 gr bullets at 3300 fps. In your case it might not be related, it seems you have a walking barrel or scope, or even scope mount issue. Check to see if you barrel free float and you crown isn't mess up, then check bases of the scope, check torque on every screw, then check you rings, check inner surface of the rings, sometimes its good idea for rings to match surface of the scope, there are few scope bedding technics. You can also try to let someone else to shoot, see if it changes anything... Good luck.
     
    Last edited: May 9, 2011
  7. sp6x6

    sp6x6 Well-Known Member

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    It is nice if you shoot strings across chrono, this sometimes help compare vertical strings with, faster and slower loads and your es. More es is usually more vertical the further the shot more noticable, horizontal tends to be wind.
     
  8. berger21

    berger21 Member

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    It would be nice to shoot a chrono when trying to verify some stringing. I do not have access to one. As far as the sand bags, I have just a sandbag for the front and a bag that was purchased from Walmart for the back, looks like a Caldwell but it probably isn't. I guess I was getting a little to confident as out of the 9 rounds I shot, 3 rounds were well under a moa and a couple more rounds were just over the MOA. I have checked torque on rifle and scope and I do use a torque wrench. I believe the problem is as one of you replied that I need to continue on my technique. The wind did not help me out, but I will work on getting back to basics. Thanks for all of your input.
     
  9. rscott5028

    rscott5028 Well-Known Member

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    Wind would easily account for much of what you're seeing.

    It also seems to me like you have too many variables changing to be difinitive.

    I suggest you pick the best 2 loads and go back and shoot several groups each.

    ... ideally using a chronograph with no wind

    If one group is consistently vertical, then the velocity ES is one consideration.

    If the other group is consistently horizontal, then seating depth/jump is something to consider.

    -- richard
     
  10. Bart B

    Bart B Well-Known Member

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    What some folks are saying about vertical shot stringing in this thread is, IMHO, way off base; probably out of the ball park.

    Consider the fact that a .308 Win. has a 2/10ths inch vertical shot stringing at 100 yards for a 100 fps spread in muzzle velocity. And a .300 Win. Mag. shooting 180-gr. spitzer boattails out at about 3000 fps with a 100 fps spread in muzzle velocity has vertical shot stringing at 200 yards of about 6/10ths of an inch. If vertical shot stringing is more than this, there's something else causing it. And a rifle capable of 1/8th MOA groups of the shooter at these ranges is needed to see these effects of a 100 fps spread in muzzle velocity.

    Most common problem shouldering a rifle as it rests on something atop a bench is where the butt plate's put in the shoulder; too low and shots go high; too high and shots tend to go lower. In second place is how hard one bears down on the rifle's cheek piece with their own head; too hard and shots go low, too soft and shots go high.

    Horizontal shot stringing from rifles so shot is common when the rifle's not pulled back into the shoulder the same way for each shot. There's also a shift in windage zero from sitting at a bench to standing up on your hind ligs; shots to to the right more so when at the bench.

    If the rifle's trigger has a really heavy pull, the impact of the trigger finger transferred to the rifle when the sear's released and the finger lever comes to a hard stop is quite a force. If that force is not in line with the bore axis, it'll pull/push the rifle to one side. Good way to see this is dry firing and watch were the scope's reticule moves when the firing pin snaps home. If it jumps left for a right handed shooter, the trigger finger's not far enough onto the finger lever; it pulls back at an angle from right to left. If the trigger finger's too far in, it pulls the rifle to the right moving the recitule that way when the firing pin snaps.

    One sure way to have horizontal shot stringing is finger flicking when the round fires. That's when the trigger finger's unconciously told to jump off the trigger's finger lever when the sear releases. You gotta keep that finger on the trigger with it at the stops until the rifle stops moving from recoil. Practice doing this so it's second nature. Finger flickers never shoot very accurate. This is called follow through.
     
    Last edited: May 12, 2011
  11. rscott5028

    rscott5028 Well-Known Member

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    Bart B makes some very good points.

    But reallistically, you've got way too many variables changing. You need to try again when there's no wind and establish a baseline.

    -- richard
     
  12. berger21

    berger21 Member

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    Again you guys have very good points. I hope to get some new loads loaded tomorrow and spend spend some time on the range this weekend. Perhaps I will have some good pictures to share. Thanks for your help!
     
  13. berger21

    berger21 Member

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    I changed rifles and finally fine tuned some loads in my Sendero 300 wm. After glass bedding it and and sending the scope back to check POI I was able to find a calm morning and did some 510 yard shooting. The group pictured is a 4 shot group at 3 and 3/8 inches. There was the 5th shot that went high and left about six inches from the group, but I'll say I pulled that shot. I think I will leave the load and the rifle alone as I'm not sure I can get any better patterns. This rifle has come a long way from 3 inch groups at 100 yards. I'm using 79 grains of H1000 powder behind Berger 185 grain VLD hunting bullets seated to 3.60 COAL
     

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  14. elkaholic

    elkaholic Well-Known Member

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    When you stick with it you can usually figure things out if the rifle is any good in the first place. Good job!......Rich