Can a scope cause issues with only vertical stringing?

[epags]

I'm acronym challenged. What is PEBCAS?

My question too. Google search brought me back to Tree Farmer's post. Come on guys don't use an acronym without spelling it out the first time you use it....that's what my military training said to do.

 

[skipglo]

So I have a new to me rifle. It had 50 rounds down tube from previous owner. I've been trying to work up a load and thought I found a decent load at 100 yards. I did a satterlee load test and found two nodes. I did a little testing on both and found
A decent load which had tighter group (.6inches at 100 yards). The others were around .8inches. So I loaded up some more of that group and took it out to 400 yards. The horizontal spread of the 3 shot group was less than 3 inches but the vertical spread was like 8 or so inches. Either I have some serious issues with extreme spread in the 3 shots or something else is going on. I know this is not a lot of info but it just really surprised me that the 3 shots were so close to each other horizontally but not vertically. Can a damaged scope do this? I'd think if the scope was damaged, it would shot gun pattern and not vertical string. I'm confident in my loading (use two scales, make sure brass is prepped etc). I was using hammer bullets with h1000 powder. Can a brake cause this? Thoughts?

Check your stock/barrel screws would be the first place I would look!

 

[Bigeclipse]

Did you adjust for drop with your turret? I just sent a brand new scope back because when I would dial dope at distance, it would gradually walk its way up shot by shot. However, it's more likely to be ES or neck tension

Yes I did adjust it. And it did get higher...shot by shot. Hmm. I wonder if it could be that. How did you determine it was that?

 

[MTbackwoods]

Yes I did adjust it. And it did get higher...shot by shot. Hmm. I wonder if it could be that. How did you determine it was that?

I just got it to repeat that at 700 yards numerous times. I ended up having to put 16 moa on to make a hit at 700 (should have been more like 12-13). Then every shot after that would walk .5-1 moa higher. Consistently. And this was with a garbage load I threw together to fireform my brass. It had a high ES but it was obvious what was going on

 

[Airedale56]

I had an old Marine Sniper Instructor point out that I was vertically stringing shots and explained the why of it during my attendance at an LE sniper school in 1988.

It was caused by a (combination of too high rings vs a too low comb combination) varying cheek weld which caused me to not have consistent eye placement behind the scope during each string.

The simple fix for the rest of the class was 100 MPH tape and a rolled-up balaclava to raise the comb to the right height. Consistent cheek weld due to proper comb height resulted in consistent eye placement which resulted in < half-minute, round groups.

OP might be experiencing a similar issue.

 

[MAD10]

Diddo what Alex and L.Sherm have said. Another way to understand ES is you could have a ridculous ES say 100 fps and still shoot a one hole group at 100 but that same load wil make you cry at distance.

Take a look at a ballistics app and plug in different velocities at say 1000 yards for a comparison. A 30 or 40 ES is like a 2" difference in a lot of calibers and you almost can't hold that 2" at 1000 yards because your reticle thickness will block your view. I have watched guys hammer steel or rocks and were surprised when crono'd read 23, 25, 42 ES.

Here is what I would do in order to eliminate things.

1) Run your load over a chronograph- if your ES is respectable than something else is causing the vert dispersion.

2) Have another known good shooter that you know can drive a rifle shoot that load at distance and see if they have similar results.

3) Drop on another scope known to perform well. I once had a new scope on a rig that had too little internal travel and it would change POA POI at different times because it was max'd out - almost made me punch myself in the face thinking I could not drive my rifle.

I am sure you know most of what has been said - just make sure you only address only one thing at a time or you'll go down rabbit holes you don't have too. Keep us posted on your findings. Good luck

ps Comb Height can cause this too. An adj cheek piece can screw you up too. Once you zero and you are sure your eye alignment is spot on then make a witness mark on your stock so that when you drop your cheek piece to pull the bolt out for cleaning etc you can return to that same cheek piece height it will cause you to hit high or low - think shotgun stuff when you think about comb height

 

[Bigeclipse]

I had an old Marine Sniper Instructor point out that I was vertically stringing shots and explained the why of it during my attendance at an LE sniper school in 1988.

It was caused by a (combination of too high rings vs a too low comb combination) varying cheek weld which caused me to not have consistent eye placement behind the scope during each string.

The simple fix for the rest of the class was 100 MPH tape and a rolled-up balaclava to raise the comb to the right height. Consistent cheek weld due to proper comb height resulted in consistent eye placement which resulted in < half-minute, round groups.

OP might be experiencing a similar issue.

Theoretically using Proper parallax should eliminate issues caused by a inconsistent cheek weld.

 

[Hand Skills]

I think proper parallax eliminates the optical variable, but it does not address the physical variable of stock contact.

The fellow who showed me how to shoot bugholes (back in the 90's) had a piece of masking tape on his stock. This was an aid which helped him achieve consistency behind the rifle. It's important to remember cheek weld is actually 2 things, position AND pressure.

I think a lot gets made of parallax by people who don't understand how it works - error is inversely proportional to distance. The farther a target is, the less error you get. It's shooters with high magnification at 10m and 25m who notice parallax the most