What Causes Vertical stacking?

[JWFilips]

Hi Guys,
While shooting what I thought to be a good light rifle load with a plain base bullet (Approx. 1300 fps) I shot an almost perfect vertical string in 10 shots spanning about 2 " in height ( some put 3 shots in one hole & 2 shots in another one hole of this vertical string. Any Idea what is going on ?
( I probably heard this answer 10 times but I just can't remember)
Thanks
Jim

 

[Rick]

I've not played with such low end rifle loads but a primer switch could prove interesting. I've cured vertical stringing with faster loads by playing with different primers. Could also check neck tension for uniformity.

 

[Brad]

What powder? I bet a small change in powder could eliminate the vertical. Often it is a matter of barrel harmonics. The muzzle is not at a node so some shots the muzzle is moving up, some it is moving down.

 

[RicinYakima]

I have to go with the Moderator's here: 1) barrel at a bad place in vibration, 2) ignition is not consistent, 3) inconsistent bullet start. Extreme spread in velocities, will not make that much difference in 100 yards. Now for the bad news, as you work on this, your 1/4" by 2" group can become a 2" round group. Oh, the fun of cast bullets! Best wishes, Ric

 

[fiver]

it can be a node issue it can also be velocity variations..
I guess the two are related if you think about it.
faster powder usually cures it, or more of the same powder, or a lot more slower powder. [or a filler]

 

[quicksylver]

Try going up a tad and down a tad...02 grs....
Also make sure your stock is in the same place..

But first try another 5 rnds...could just be "the day"...

 

[KHornet]

Far to many variables for anyone to have an exact answer to your specific question Jim.
All, or a combination of the few suggestions could/might/maybe be the answer, or then again,
maybe not. Like Quick said "could just be "the day"! I equate that to the "Women have bad
hair days, and we have bad shooting days!"

 

[quicksylver]

It's not the velocity...if I can find the target I have a 5 round "string of beads" group fired with my AR .223....if i remember correctly they are about 15 degrees off dead vertical...they were doing about 3000 fps

 

[Ian]

Jim, usually it means you're about half a grain (or less with pistol/shotgun powders) away from your magic load. You WANT to see a tight vertical during your workup, it means you're almost there. Go past it and you'll get a scattered round group if all else is as it should be. As most everyone else said, the cause is likely barrel harmonics.

 

[Intheshop]

Sort of,all the above....

Always a good practice working on your bench etiquette.The idea being it applies to the next rig/rifle as well.One major reason BR guys are at the top velocities,isn't just external ballistics.The recoil pulse with cast usually is a softer,longer "tug" on the rifle/bag connection.So you simply have to be "better" on the bags vs high end,speedy JB loads.

 

[popper]

light rifle load with a plain base bullet (Approx. 1300 fps) @ 100 easily fps. Depends on powder/fill/filler, etc. Or, for guys like me with a shot shoulder, muscle relax on bang. Typically caused horiz. also.