Vertical stringing---Causes?

[hank shaper]

What in your shooting technique would cause vertical stringing? I placed my sandbag under my rifle barrel shank. The barrel is 27.5" #5 contour. I know that some cartridges will string vertical if loaded too hot. These were not overly hot (no usual pressure signs). I am not a benchrest shooter and I am questioning my set up. Advice?????

 

[41mag]

[ QUOTE ]
What in your shooting technique would cause vertical stringing? I placed my sandbag under my rifle barrel shank.

[/ QUOTE ]

If I am reading this and understanding it correctly, then you would have your barrel resting on the bag?

If this is the case it would contribute to your problem. If your in fact referring to having the forend of the stock on the bag, then it is from a different cause.

With the barrel resting on the bag the pressure will be different for each shot. This will cause a change in impact on your targets, similar to if your barrel is in contact with the stock.

Course seein what time it is I may not be comprehending what your referring to exactly either. /ubbthreads/images/graemlins/grin.gif

 

[Chawlston]

[ QUOTE ]
What in your shooting technique would cause vertical stringing? I placed my sandbag under my rifle barrel shank. The barrel is 27.5" #5 contour. I know that some cartridges will string vertical if loaded too hot. These were not overly hot (no usual pressure signs). I am not a benchrest shooter and I am questioning my set up. Advice?????

[/ QUOTE ]

Put the bag under the recoil lug.

James

 

[jb1000br]

might help...

http://www.6mmbr.com/verticaltips.html

JB

 

[NYLES]

Ive found that with vertical stringing, add powder. As long as you are not seeing pressure signs. And nothing should be touching the barrel.....NOTHING!

 

[NYLES]

Good article1 /ubbthreads/images/graemlins/wink.gif

 

[Fiftydriver]

I think what is ment by "bag is under the barrel shank" is that the front bag is under the stock in the location of the barrel shank, just ahead of the receiver. May be wrong but that is what I took from it.

Some questions:

What is the rifle chambered in?

Does it always string vertical?

Does it start printing shots low and then go up or do they start high and walk down or is it random, just in a vertical line?

Has the rifle been accurized?

Is the barrel free floated?

Is this a quality barrel?

Is the receiver bedded to the stock?

There are so many things that can cause vertical stringing its hard to pick just one and say thats the reason without looking the rifle over.

In my experience, the single best way to get vertical stringing with a conventional opposing bolt lug receiver like most of the modern factory receivers is to have one bolt lug contacting the receiver but the other partially or totally floating.

With very low pressure loads generally accuracy is quite good all else checking out that is. As pressures increase you will see vertical stringing become much more appearant. This is a good reason to have the receiver totally accurized and then lap the bolt lugs into 100% SQUARE contact.

Also, if the barrel channel of the stock is touching the barrel, as the barrel heats up you will often notice your groups walking on you. The direction the shots walk are determined by where the barrel is contacted.

I would say 95% of the time, this is caused by something mechanical with the rifle. Poor machining, poor bedding, contact with the barrel. Very seldom have I found that adding pressure to a load will cure this problem. Generally it willmake it worse.

When adding powder to a load improves accuracy, this is generally because the bullets are not hit in the rear with enough pressure to cause them to bump up and seal the bore consistantly from shot to shot. This can be seen most often in factory rifles which are not held to much of anything as far as bore specs are concerned.

First place I would look would be your bolt lugs, then to see if the barrel is on contact with the stock anywhere.

Answer the above questions and it will help us point you in a more definate direction to what may be causing this.

Kirby Allen(50)

 

[hank shaper]

Fiftydriver you read right. I will answer your questions in order. 6.5X300WBY First time to the range. High then low for the most part. Rem 700 has been trued. Barrel is free floated. Lilja 27.5" 1 in 9. Bedded in syn stock with epoxy steel including about 2" of the barrel shank. This reamer has a long throat. All of my bullets are well off of the lands due to mag. restrictions. I shot several powders, most all loaded to the point of showing slight pressure signs. It has been my experience that the big magnums print better when loaded hotter. I shot two flat base bullets that printed better. They were pretty hot also. I shot 130 gr. Sciroccos that all printed vertical with almost all powders. My loads are as follows:

VV 160 75.0 grs. with 120 gr. FB Sierras 3/4" @ 100
Retumbo 77.0 grs. with 130 gr. Horn FB 3/4" @ 100
H 1000 80.0 grs. with 130 gr. Scirocco
AA8700 89.0 grs. with 130 gr. Scirocco
H5010 84.0 grs. with 130 gr. Scirocco This is too lite
H 1000 85.0 grs. with 120 gr. TSX
VV160 71.0 grs. with 130 gr. Scirocco

My lateral spread makes me think this gun wants to shoot. The inconsistent vertical makes me think it might be my technique, although this has never been a problem with my other guns (7 STW, 300 win and 280 AI).

Thanks for everyones imput and especially these detailed questions Fiftydriver.

Hank

 

[hank shaper]

Fiftydriver,
I will be out of touch till Monday. Let me know your thoughts. Gonna catch the last weekend of doe season here in Texas.
Thanks for the help!
Hank

 

[Buffalobob]

The gun is trying to tell you it does not like brocoli. It much prefers green beans.
I would quit trying to force the Sciroccos on it and give it more Sierra's.

 

[Fiftydriver]

First off, with these big capacity, medium/small bore rounds, small things make a big difference. First thing I would do, forget about the magazine length at this time. You want to get the rifle to shoot and it will only shoot what it wants to shoot.

You can not make it shoot a load of your choice.

Drop your load back, and seat those bullets up to the lands, within 10 thou or so to start with and rework up your load from there and see if you get any better results.

In most cases seating bullets well off the lands is not a good idea for consistant accuracy. Sometimes it works, most times, not so much.

I would also agree with BB, it appears that your rifle prefers conventional cup jacketed bullets, again ya gotta give her what she wants.

I am not a huge fan of the Scirocco bullets. On paper they look great and in rifles that shoot them they are great performers but they are very sticky because of their pure copper, thick jacket and top end velocity is hard to reach at comfortable pressures. This comes out even more with the large case capacity rounds like yours.

If you want a bullet of this design, order some of the new 130 gr Accubonds and give them a try but again, it appears that your rifle prefers the conventional cup jacketed bullets.

I would play with the 142 gr SMK or 140 gr A-Max and see what they do seated to the lands. I have always found that in these large case capacity rounds that the heavier the bullet you use, the more consistant the rifles are on average. You have plenty of HP to get the 140 class bullets to 3300 fps. Ballistically they will out shine the lighter pills at long range.

If they shoot seated longer, you can always have the receiver modified to accept a Wyatts extended mag box which will allow up to 3.820" or 3.910" of OAL depending on what model you get.

Hope this helps.

Kirby Allen(50)

 

[Chawlston]

LIsten to what Kirby is telling you. He is basically saying that since the Swifts have more copper, they are harder to squeeze than bullets with more lead. The harder the squeeze, the higher the pressures.

James

 

[specweldtom]

If I read right, you're stringing 3/4 moa vertical. That isn't real bad for a high performance round, but is very discouraging. Are you are deburring the flash holes in your brass? Doing so has reduced vertical stringing on the few rifles that I have done it for, from 7-08 to 338x378. If it's Norma brass, it usually has good holes, but not perfect. Also, is the bottom surface of the recoil lug clearanced off the bedding? The location of the Remington front action screw can make a fulcrum out of the bottom of the lug. Additionally, if any part of the screws touches the bore of the pillars, it can make the rifle a little squirrely, usually not just vertical tho.
As a last resort, you might try re-crowning in very small increments, but I don't recommend it for vertical stringing until nothing else has worked.

I would be very very cautious about moving the bullet out. I like to load magazine length ammo that is hot, and let the freebore work.

I will be watching this thread with interest, because I have experienced 4-5 to 1 vertical dispersion too. I hesitated to post because some heavy hitters are already on the case. Let us know what works.

Have fun, Tom

 

[hank shaper]

I am shooting the Nosler 300 WBY brass. Most of the detailing has been done. The lug is clear. I was told by a benchrest shooter to move my front bag forward about 3" of the barrel shank. He said on longer barrels (mine is 27.5") this can help sometimes. I have a lot of little things to try. I'll keep you all posted as thing progress.

Thanks to all,
Hank