Horizontal group dispersion

[racesnake]

Seems like every time I go to the range to check out a new powder or bullet I'll get at least one group that spreads horizontally. I first thought it was me jerking the trigger or not holding the same for each shot. I have since started rechecking the same loads again and found that most of the time they will horizontal again. Can anyone explain, I'm baffled.

 

[Terry]

1. Wind
2. Paralax adjustment.

 

[XTR]

Seems like every time I go to the range to check out a new powder or bullet I'll get at least one group that spreads horizontally. I first thought it was me jerking the trigger or not holding the same for each shot. I have since started rechecking the same loads again and found that most of the time they will horizontal again. Can anyone explain, I'm baffled.

Usually horizontal is the shooter. I don't know your technique and I'm no BR shooter. I've found cheek weld/pressure will do a lot to your horizontal, holding the rifle on the POA vs having it rest on the POA will induce horizontal, trigger control/grip and finally your shoulder angle and differences in pressure on the butt of the rifle.

 

[Alex Wheeler]

Barrel harmonics.

 

[savet06]

In my score gun when I get a load that will spread horizontally it is usually too wind sensitive and I need to go up in charge to induce a little vertical in it. Gene beggs also found that horizontal can be induced because the bullet is seated too far into the lands and needs to be backed off a bit. When a group goes flat like that you will be able to get lucky if there is no wind but rarely does that happen for long. At 100yds i like to have 1/2 a bullet or so of vertical and a little more at 200yds otherwise I get blown right out of the 10 or pushed out of a group. As they say up north. "More powda!"
Is the group a fairly flat horizontal shape?
Mike

 

[mshelton]

Kinda like Savet06 said, try monkeying with the seating depth.

 

[M-61]

Had the same problem when starting with a 6BR. The end result was loads that were on the light side by quite a bit. This site suggested that, and as I carefully worked my way up the horizontal stringing stopped. I went thru all the standard checks...trigger pull, position etc.,
and the increased load did the trick. Caution as you go up!

 

[racesnake]

What's so frustrating, is that when I increase/decrease the load I get away from the horizontal but the group usually is bigger than if I could get the horizontal group to bunch up i.e., come together. I never thought about varying the seating depth - that could be the answer..

 

[savagedasher]

If you don't have much vertical the powder charge is close . I would check the bedding front and rear bags .Allot of the time it is you.Normally horizontal is caused by the gun being moved sideways check to see if your pushing or holding the rear bag.I find most of the time it its the shooter.Bad or in-concent gun management Let someone that shoot good try if it gone .its not the gun or the load. Good Shooting Larry

 

[BoydAllen]

I think that you have good answers in the suggestion to try very small adjustments in seating depth. If you are interested, look on Youtube for Jack Neary. There are six segments of a tuning and match strategy talk that he gives at some benchrest matches, that I think that any serious bench shooter would benefit from watching and taking notes from. What he said agrees with some of the posts on this thread, but there is more, that is well worth your time. Tony Boyer also mentions what you have experienced in his book.

 

[racesnake]

Thanks for all the tips, fellows. I've started watching the Jack Neary videos and they do contain a wealth of useful info, Boyd. Cheers.
Dave

 

[BoydAllen]

;D

 

[amlevin]

Barrel harmonics.

Definitely. Sometimes the matter is oversimplified with people stating that "Vertical is Load", "Horizontal is Shooter or Wind".

Remember that barrels don't just vibrate up and down, they also move sideways as they react to the shock wave. The muzzle usually follows more of a lissajous curve such as this:

Tuning merely adjusts the barrel movement by timing the shockwave so that the bullet is released each time at as close to the same point as the last shot. Now which one was it? 8)

 

[BoydAllen]

I disagree. While uniform velocity will have bullets exiting at the same place in the muzzle's vibration pattern, you can have that, and still be out of tune. Also, your drawing is wrong. Because the barrel is loaded in the vertical direction during firing, by the rifle rotating around its center of mass, the motion motion of the muzzle is more vertical than horizontal. You might want to pick up a copy of Rifle Accuracy Facts, by Harold Vaughn. Horizontal is not always wind, but the wind is an important factor that is too often ignored by shooters who kid themselves into thinking that they only test when the wind is not blowing, but do not have any way to see what it is doing between their position, and the target. As far a vertical goes, with an accurate rifle, it has been my experience that it may be changed by working with charge weight, but that this is not the only factor. For example, friend that was shooting a rifle with quite a bit of angle on the bottom of the butt stock, found that by taking my advice and shouldering the rifle solidly that he cut his vertical in half.

 

[bigedp51]

I do not have any expensive target rifles and the closest I can come to that is owning a cheap Stevens 200 bolt action with a 26 inch heavy barrel in .223.

What I do know from collecting the British Enfield rifle is this:

A military rifle is tuned to standard issued military ammunition, and on the Enfield rifle it is controlled by up pressure at the fore end tip. If you loose up pressure on the fore stock you will have vertical stringing. If the butt stock becomes loose you will have horizontal stringing.

I do not have BoydAllen's experience and knowledge but I would like to make two sugestions. :

1. Mix a little Viagra with your powder and see if it stops the barrel from flexing.

2. If the barrel remains stiff for over four hours DO NOT call a gunsmith.

I have seen this someplace before, I think it was an early 1960s TV program............

Now I remember.............................

There is nothing wrong with your rifle............
We will control the horizontal. We will control the vertical......................
We repeat: there is nothing wrong with your rifle............
You are about to experience the awe and mystery which reaches from the inner mind to — The Outer Limits.

 

[bigedp51]

I have one more suggestion.........

Don't try and be a cool cat and listen to rap music when your shooting from the bench.

Now watch the barrel vibration and movement in the vedio below.
Free Float Barrels

http://www.youtube.com/watch?v=Rte7K_yRTUI&feature=youtu.be

Remington 700 Varmint Rifle Barrel Tuner Demo
http://www.youtube.com/watch?v=DhRIebOY4Jk

Barrel Tuner Vibration Analysis:
Effects of tuner adjustments on vibration frequency
and the shift in barrel node points.
http://www.varmintal.com/atune.htm