What causes vertical stringing?

Dave42

Dave42

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I'm not new to shooting or reloading but I am having a problem with one of my rifles and thought I'd ask. I understand that it is most likely due to a velocity spread but what are some of the causes and fixes that you guys have seen.

I've tried alot of different things now and I'm ready to give up on this barrel but thought I'd ask to see if there is anything I've missed.

Thanks

Dave

The gun is a custom rem 700 6.5/284. The barrel I had on it before this one shot just fine.
 
I would have said it is velocity spread. It might be your barrel contacting with the stock or it could even be you cheek weld. I hate those curse-ed problems that mess with your head. If you said it is the second barrel on this rifle it could be contacting. Things like this suck because now you second guess yourself and your rifle. This is one thing you never want to do because now you don't trust your rifle. It is always in the back of your mind when you are shooting and now is becomes a mental game. I would check every thing on the gun, scope mounts, action screws, maybe change primers. Once I have done all this and the problem still occurs then change yourself. Stock weld, how hard you hold the gun, where you put your thumb on the back of the palm swell.

The only way sometimes to cure this is to get a friend to shoot the gun and see what his groups are like. Or just shoot the S*%t out of it. This works for me but the barrel does not like it.:)
 
Full benchrest with bags front and back obviously:

Load up 4 rounds .2 grains lower and 4 rounds .4 lower. Do the same higher if you're not at the max for that rifle.

Shoot at different bulls at 200Y targets and shoot one from each different load till you're done. Watch barrel heat so allow cooling time. Post back the change in vertical.

(I load up 2 more of my regular load and fire them off first at whatever to warm and foul the barrel then start with my testing)

Mike
 
complete article on 6mmbr.com

Abstract:
Speedy Gonzalez, noted shooter, gunsmith and recent inductee into the Benchrest Hall of Fame, offers these pearls of wisdom to help you eliminate vertical in your shot strings. Remember that vertical can result from myriad gear issues and gun-handling mistakes. Try to isolate one item at a time as you work to improve your groups.
Click to expand...

here's the complete article:
http://www.6mmbr.com/verticaltips.html
Very interesting article, I think I read it every other week just to stay on the edge!
 
In my experience vertical stringing is two things. Rifle looseness - everything hanging on the barrel of my SVT that isn't tight causes it to string. Secondly, head position - unless you are freakishly consistent putting your head and eyeball back in the same place shot after shot, you will not see the target the same way and shots will string.
 
is your barrel free floated? check for something underneath, dirt debrise, i had a pine needle in there and same happened to me v/string. asked same question to gunsmith he said to check same. shoots fine and everytime out i run a fresh fiver dollar bill down under the barrel. just something to look at. and i agree with the one statement about "looseness" properly torq your bolts, to ensure consistency.
 
Bedding, incorrect powder charge, improper follow through.

For load tuning tips, have a read on my website in the rifle tech section.

If you are running a powder charge less then 85% load density, try a slower powder and get as close to 100%. It helps.

Accurate weighing of charges will help alot too.

good luck.

Jerry
 
Thanks for the help guys.

I've ruled myself out cause I have another rifle nearly identical with no problems. I have not checked the torque on the action screws so that is a good one. The barrel if fully floated and the bed job is probably the nicest one I've ever seen so no worries there.

I'll try a few of the suggestions here and let you guys know. Thanks again!
 
By stringing, does it walk from one edge to the other, or are they randomly dispersed along a vertical line? In other words does shot #1 start at one end, and #10 is at the other end of the string?

Shots that walk from one edge to the other are doing so because something is changing as the barrel gets hotter. It may be the barrel has stress or asymmetry, it may be bedded so that part of the barrel is impinged. Bedding on any part of the barrel acts as a heat sink and causes asymmetrical heating/cooling=warping.

check your bedding contact, tighten and torque all your action screws. Repeat your test by shooting one round every 2 minutes and see what happens.

If you have random vertical dispersion, you most likely have inconsistent velocity
 
I may have found the problem and it does have something to do with the bedding. I'll post more once I've done some testing.

The stringing does seem to be temperature sensative though. The gun shoots about 4" groups at 700m once it has warmed up but starts about 10" higher on a cold bore and jumps up and down untill it settles out and starts to group.
 
Obtunded said:
By stringing, does it walk from one edge to the other, or are they randomly dispersed along a vertical line? In other words does shot #1 start at one end, and #10 is at the other end of the string?

Shots that walk from one edge to the other are doing so because something is changing as the barrel gets hotter. It may be the barrel has stress or asymmetry, it may be bedded so that part of the barrel is impinged. Bedding on any part of the barrel acts as a heat sink and causes asymmetrical heating/cooling=warping.

check your bedding contact, tighten and torque all your action screws. Repeat your test by shooting one round every 2 minutes and see what happens.

If you have random vertical dispersion, you most likely have inconsistent velocity
Click to expand...


What about horizontal stringing Obtuned? I follow this thread but I do not suffer of vertical stringing, my groups are flat but spread horizontally.
Poor benchrest technique? Bad wind reading? At one point I tought it could be because of a factory trigger pull too heavy... :confused:
And no, my horizontal stringing does not walk, it's random...
 
Same thing - Barrel is bending due to uneven thermal expansion/stresses, causing shots to "walk" as the barrel warms up. A random dispersion in a line can be caused by other things, including velocity spread, or just plain ole barrel whip.
 
Dave42 said:
I may have found the problem and it does have something to do with the bedding. I'll post more once I've done some testing.

The stringing does seem to be temperature sensative though. The gun shoots about 4" groups at 700m once it has warmed up but starts about 10" higher on a cold bore and jumps up and down untill it settles out and starts to group.
Click to expand...


Hey Dave,
Those barrel threads work in reverse too. I'd pitch that barrel and see if the new one is easier to get along with. Life's short enough as it is.
 
charles.emond said:
What about horizontal stringing Obtuned? I follow this thread but I do not suffer of vertical stringing, my groups are flat but spread horizontally.
Poor benchrest technique? Bad wind reading? At one point I tought it could be because of a factory trigger pull too heavy... :confused:
And no, my horizontal stringing does not walk, it's random...
Click to expand...


If the vertical is good and you have random horizontal dispersion, I would

a) Try on a dead calm day at short range ~ 100 yds (is it wind/mirage?)

or

b) Let someone else have a go (Is it your technique, trigger and lack of follow through?)

I just finished shooting a match in Nanaimo where the flags were dead limp. At 300M we were being pushed almost a minute from one side to the other by mirage.

It is possible for barrel warp to cause horizontal (or oblique or vertical) but it tends to walk rather than spatter.
 
CE, if the accuracy of your horizontal group is within the expected performance of barrel, rifle and load, you have a great load which will work superbly at LR.

However, I am guessing you are seeing horizontal spreads wider then desired.

My guess is that wind is what is causing the movement. As was alluded to, you can have flags showing NO WIND but the reality is that there is air movement which will push a bullet around ALOT.

Keep an eye on the mirage and shoot when the movement is the same. Compare that with flags and you will have a great chance of getting similar conditions. The groups may be off center but that doesn't matter as long as all the shots go in the same place.

how 'thick' is the group?

Jerry
 
I would say my vertical spread is sub-inch but horizontal spread is often as large as 2 inches at 100yd
 
I have vertical stringing as well. Cold shot is high, than they work down to a consistent after 4 or so shots and barre isl quite warm. Is there any way to minimize that. All is tight by the way. Savage .300 win mag.
 
fn, do the reverse. If the cold bore is consistently in the same place, then make that your sight in point. Limit to 3rds and tune your load for that.

Keep the barrel cool and your groups will be consistent.

Jerry
 
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