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What causes horizontal and vertical strings

 
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  #1  
Old 05-08-2011, 09:28 PM
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Join Date: Feb 2011
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What causes horizontal and vertical strings

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.
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  #2  
Old 05-08-2011, 10:16 PM
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Join Date: Dec 2008
Location: Grantsville Utah
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Re: What causes horizontal and vertical strings

Quote:
Originally Posted by berger21 View Post
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.
It could be any number of things but I would try changing the seating depth and see what happens......Rich
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  #3  
Old 05-08-2011, 10:31 PM
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Join Date: Feb 2011
Posts: 8
Re: What causes horizontal and vertical strings

I can only shorten them as I am loading 3.34 and this rifle has a detachable magazine and factory loads are maximum length.
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Old 05-08-2011, 10:42 PM
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Join Date: Dec 2008
Location: Grantsville Utah
Posts: 3,482
Re: What causes horizontal and vertical strings

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
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  #5  
Old 05-09-2011, 04:49 AM
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Join Date: Jan 2007
Location: PA
Posts: 1,095
Re: What causes horizontal and vertical strings

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.
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  #6  
Old 05-09-2011, 06:00 AM
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Join Date: Aug 2009
Posts: 693
Re: What causes horizontal and vertical strings

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 by Jinx-); 05-09-2011 at 06:06 AM.
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  #7  
Old 05-09-2011, 01:36 PM
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Join Date: Dec 2009
Location: NW MT
Posts: 2,654
Re: What causes horizontal and vertical strings

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.
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