Vertical POI shift. What’s causing it?

[Matt Corbell]

6.5 creed Barnes vortex 127 LRX factory ammo. Thoroughly cleaned bore of all copper and carbon. All screws on action, scope, and mount are tight. Rifle is dead on left & right. But shots will string 3” vertically. Any ideas?

 

[dchum]

6.5 creed Barnes vortex 127 LRX factory ammo. Thoroughly cleaned bore of all copper and carbon. All screws on action, scope, and mount are tight. Rifle is dead on left & right. But shots will string 3” vertically. Any ideas?

What scope?

Is it a steady incline in elevation? Or does it go back and forth?

Shoot a 10 shot group. I know that seems like a lot but that will give you a true picture of what’s going on.
3 shot group can give off the perception of a pattern but really just adds to the confusion.

Unfortunately I have never seen that bullet group very well.
I would bet the rifle just doesn’t shoot the load well enough.

 

[Hogpatrol]

Scope brand and model?

 

[TMac]

Pressure point between barrel and stock when the barrel warms up is a possibility. If you are shooting 3 shot groups, try 5-10 and see if a more normal pattern develops.

 

[whisk(e)y hunter]

Could be the ammo too, combined with varying barrel temp as it heats up/cools off unless you’re shooting every shot cold

 

[Schüler Jumbo]

Barrel contacts stock causing vertical stringing. In lieu of circular oscillations which shoots a triangular pattern the uneven pressure point causes vertical stringing. Had the exact same problem on a custom built .375 H&H.

 

[Tbitty]

As others have said, try larger group samples to get a true pattern. If starting cold bore, shoot a few warm up shots then go for group.

Or try a different type of ammo. That should tell you quickly if its the gun or the ammo stringing

 

[USMA84DAB]

Are you using a cheekrest such that you can anchor your cheek bone is in the same place each shot? Are you moving off the rifle between shots/placing your melon back on the rifle in a different position? Both of these can string your impacts.

Lots of other good possibilities above as well.

 

[mark-hunter]

6.5 creed Barnes vortex 127 LRX factory ammo. Thoroughly cleaned bore of all copper and carbon. All screws on action, scope, and mount are tight. Rifle is dead on left & right. But shots will string 3” vertically. Any ideas?

Two things come to mind.
Clean barrel needs some number of fouling shots till gets stabilised.
Shoot some more.

Winter and summer shooting.
If you zeroed at winter, then it is possible it will shoot high at summer and vice versa

 

[dchum]

Two things come to mind.
Clean barrel needs some number of fouling shots till gets stabilised.
Shoot some more.

Winter and summer shooting.
If you zeroed at winter, then it is possible it will shoot high at summer and vice versa

It’s vertical stringing not a POI shift upwards.

 

[Choupique]

From a technical perspective, pressure on the barrel can cause it as well as an improperly stress relieved barrel or one that is non symetrical. All different forms of the same thing. Barrel contact is an obvious one, residual stresses in the barrel cause the same effect - internal pressures in the steel bend it with temp changes.

As has been said, shoot a 10 shot group and check for barrel contact. If theres no contact and fhe impacts walk up with heat and back down as it cools, its a barrel problem.

 

[Hififile324]

If you are shooting off a machine rest with a bag, or sandbags up front, make sure your front sling swivel stud is not grabbing the bag or rest while the rifle is in recoil. That will cause the barrel to rise before the bullet fully leaves the bore causing high stringing. When we shoot the hunter rifle matches we remove the front swivel stud.

 

[lawrence_court]

Are you using a rear bag?

I've found that a vertical string (especially one that creeps throughout the group) is often caused by the butt changing position throughout the group.

Try packing a rear bag down tight and then shoot the group again.

You can also work out if it's a hardware problem by seeing if the poi is continually moving up or if it is just moving up during the shooting of a group. If it's returning to zero at the start of each group, it would suggest the hardware is ok.

 

[Rimbaud]

What type of barrel, rifle? All the advice here is excellent. I would only add something on fundamentals. Settle yourself behind the rifle, establish natural point of aim, and then take one perfect shot, 10 times, w consistent trigger pull, etc. You’ll solve the puzzle soon.

 

[Matt Corbell]

Scope brand and model?

Vortex Razor HD LHT 3-15x50. The rifle shoots 143 ELDX into a ragged hole at 100.

 

[Matt Corbell]

What scope?

Is it a steady incline in elevation? Or does it go back and forth?

Shoot a 10 shot group. I know that seems like a lot but that will give you a true picture of what’s going on.
3 shot group can give off the perception of a pattern but really just adds to the confusion.

Unfortunately I have never seen that bullet group very well.
I would bet the rifle just doesn’t shoot the load well enough.

I shot a 12 shot group and they were all in a vertical line. They shots go back and forth (up and down)

 

[Matt Corbell]

Are you using a rear bag?

I've found that a vertical string (especially one that creeps throughout the group) is often caused by the butt changing position throughout the group.

Try packing a rear bag down tight and then shoot the group again.

You can also work out if it's a hardware problem by seeing if the poi is continually moving up or if it is just moving up during the shooting of a group. If it's returning to zero at the start of each group, it would suggest the hardware is ok.

Yes I’m using a rear bag

 

[Choupique]

Im intentionally ignoring the scope and the shooter and ammo, all can obviously cause this as well.

Alternating high/low, or POI walking up with heat and back down with cooling?

Alternating back and forth is probably not a barrel stress issue. POI "walking" with temperature is a barrel problem, usually external pressure on it but can also be internal stress problems.

 

[Matt Corbell]

What type of barrel, rifle? All the advice here is excellent. I would only add something on fundamentals. Settle yourself behind the rifle, establish natural point of aim, and then take one perfect shot, 10 times, w consistent trigger pull, etc. You’ll solve the puzzle soon.

The rifle is a semi custom build by Alamo Precision Rifles with a blueprinted REM 700 action. Barrel is a Douglas. Don’t know the contour exactly but I would call it a heavy spotter.

 

[Rimbaud]

The rifle is a semi custom build by Alamo Precision Rifles with a blueprinted REM 700 action. Barrel is a Douglas. Don’t know the contour exactly but I would call it a heavy spotter.

I would contact the maker. A friend was in a similar situation with a custom barrel/rifle. He had to send it back for a tune-up. Turned out there was an issue with the assembly and with the barrel.