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Thread: What Causes Horizontal Groups?

  1. #1
    Join Date
    Jun 2010
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    What Causes Horizontal Groups?

    I recently went to the range to test fire some new loads out of my .325 WSM. I shot a 3-shot group at 100 yards using the new Reloder 17. The first shot was at 6 o'clock, the second shot was 1 1/4" to the right, and the third shot was also to the right opening up the group to 2 3/8". The temp was 88F and high humidity. The wind was 0-5 mph. The three shots didn't vary 1/8" vertically. I then decided to try a different powder, H4831sc. The three shot group was nearly identical to the group fired with Reloder 17. Then I switched powder to H4350. This proved to be a much better choice. The first two rounds were approx. 3/4" apart horizontally and the final shot dropped and opened up the group to 1 1/4". Still not to my liking but I think I can work with this powder and bullet seating depth to improve upon. Why did my 3-shot groups go horizontal using the first two powders?

  2. #2
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    Wind and bench technique are my guesses. It has nothing to do with the load. At this point all your loads are equal.

    al

  3. #3
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    Jun 2010
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    Is there another explaination?

    The wind was so light I don't see how a bullet could possibly drift that far at 100 yards. I have shot benchrest for a number of years and am capable of shooting groups under .200 at a hundred yards with my bench rifle. The one thing that puzzles me that with each shot fired the bullet kept drifting farther and farther to the right. The temperature was 88F, and after just three shots the barrel was pretty hot. I allowed the barrel to cool off in between each three shot group fired. Isn't H4350 known for its resistance to temperature change? Any other thoughts or comments?

  4. #4
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    Try a different scope

  5. #5
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    hmmmmm, well that certainly resets my perspective! If you shoot BR then hmmmm

    Although these WSM's do whack one about some......

    I'm at a loss. I've done some temperature testing of late, specifically with WSM's and more specifically focusing on H4350, VARget, RL17 and some assorted ball powders and am currently of the opinion that the whole concept of certain powders being "less temperature sensitive" is overblown advertising hype.

    As are claims of increased velocities for certain powders, like RL 17.

    But I digress:

    I still do not think it's got anything to do with the loads, nor do I think the barrel is walking.

    I do know one thing, for MYSELF shooting something this brutal for real accuracy requires a lot of setup and technique changes from the automatic bugholes of a PPC..... lucky for me I'd just gone through several years of hysteria trying (and finally succeeding) to tame my new 6X47L tight twisters... HEAVY rear bag and weight in the butt did wonders for me. They twist and bounce and hare of in sidewards directions for me....

    I'm currently putting together a 325.... Bartlein barrel, Manners stock, Borden action, designed around 200-220gr bullets should make a killer walkaround elk slayer IMO. Now if Barnes would just step up to make a real bullet........

    Keep us posted on the horizontal..... hope somebody else can help.

    al

  6. #6
    Join Date
    Jun 2010
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    Thank you for your input. I think I am going to retry these same loads again and see if it repeats. But this time it will be on a day when the temp is at or below 70F. I expected that all three of these loads would have produced groups under .75" at 100 yards. I am still perplexed by the HUGE groups I got. The scope I have mounted is a Leupold Var-X III variable with 3-10x. The rifle is a Winchester Model 70 with a stainless steel 24" barrel and a 1:10 twist. The load I was shooting in it was an IMR-4350 that produced 1/2" groups pretty consistantly. I like to experiment with different loads and thats all this was about. I thought if I could learn something from this that would be great.

  7. #7
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    Jul 2007
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    Sth Australia
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    ?

    bedding?

  8. #8
    Join Date
    Jun 2003
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    Hondo, TX
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    I have had the same thing happen.
    At the last match some of the guys looked at the groups and between large horizontal stringing and a couple of groups looking like they were shot from a 410 shotgun they decided it was the scope.
    This scope had work done to it in the form of having the plastic screws one in bottom and one in left side. We backed the screws all the way out and it seemed to settle down. I will be going back to the range for a little practice and hopefully borrow a scope this weekend and we will find out for sure.

  9. #9
    Join Date
    Jun 2010
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    I have not ruled out my scope as a possibility. If I get similar results during my next outing at the range I will replace the scope and see if that takes care of it. Thanks for your response.

  10. #10
    Join Date
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    Two more ideas on the scope.

    Parallax and/or play in base.

    If the scope doesn't have adjustable parallax it's probably unshootable at 100yds..... I recently went through this with several Leupolds.

    And bases..... Harold Vaughn illustrated a test where he tapped the bases right and left with a small hammer and fired two separate groups. I tried it and was quickly convinced.

    I now bed my bases and screws and assemble everything with powdered rosin on the base surface, oil on the screw threads. And of course Kokopelli's all the way.

    al

  11. #11
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    al,
    I think you touched on it. I assume this is a hunting rifle with the usual pencil thin barrel. If so, then the barrel is probably walking due to heat build up.

    Wildman,
    You didn't say but how long did you wait between firing the loads with different powders? I would bet the bore in not concentric with the outside diameter of the barrel. I had a 30-06 once that did exactly the same thing. It would walk the bullets across the targets to the right. If I kept shooting it would eventully settle down more or less. This was with a barrel that had been recontoured so I am pretty sure the bore was not centered somewhere about half way down the barrel. I never did get rid of all of it, but by using a lot of fore end pressure I was able to lessen it to a degree that it was useful for hunting purposes. The WSM will put a lot of heat in a barrel in a very short time period.


    Donald

  12. #12
    Join Date
    Jun 2010
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    9
    Al,

    The scope I have does not have a parallax adjustment on it. So I suppose it could possibly be my problem.

    Don,

    You brought up an interesting point...something I hadn't thought of. This is a hunting rifle with a standard Winchester barrel. I did fire each three shot group within approx. 1 -1 1/2 minutes of time. The barrel was quite hot. I then waited for approx. 10 minutes before I shot my next three shot group. Long enough that the barrel was nearly normal temperature. That would explain why the first shot was always at 6 o'clock and then each shot after would go further to the right. The last group fired with H4350, which had the tightest group, I remember taking extra time in between shots for it to cool because i felt that heat was a factor in my previous two three shot groups. This will be something I will look for the next time I go to the range.

    Thank you all for your input.
    Last edited by Wildman; 06-02-2010 at 06:34 PM.

  13. #13
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    Brisbane, Australia
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    If you want to avoid parallax with a non adjustable scope, find a cap that fits over your eye piece (some of those juice bottle tops go close) & punch a " or smaller hole in the centre of it.

    Stops you moving your head far enough for parallax to become an issue, though it can be a bugger acquiring the target.

  14. #14
    Join Date
    May 2005
    Location
    MD Eastern Shore
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    54
    The last time I had a set you drinkin' case of horizontal grouping, it turned out to be a bedding issue, cant remember what it was but I beleive it was a tiny discrepancy , like a spec of overflow in the poured bedding. Groups varied from 2" to 4" horizontal and about 1/4" vertical @ 100 yd. A careful exam of the bedding with a magnifying glass might be fruitful.

  15. #15
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    Nov 2006
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    Augusta, Maine & Palm Coast, Fl
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    Horizontal

    Something we have realized since messing with tuners is barrels will sometimes deliver horizontal groups. I have seen this in a tunnel where there was no wind so I know it isn't always a "weather Report". horizontal can be tuned out as well as vertical and diagonal vertical. Lots of everything gets blamed for what the barrel is giving us.

    Something I have noticed over the years I have been testing for the best load for BR rifles is sometimes certain loads at certain seating depths will give horizontal but it goes away with a different seating depth. There is a lot more to tuning than the platform and barrel.
    Last edited by Pete Wass; 06-02-2010 at 10:19 PM.

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