Weird Horizontal stringing of groupings..

[EricCartmann]

Wonder if anyone else experienced this..

Had a weird incident at the range this morning. We used the same load for 3 different rifles, and all 3 rifles had groupings that spread horizontally. When we changed up to different ammo, our groupings returned to normal for all the rifles. Not great groups, but a circular kinda of pattern and not a straight line horizontal pattern.

This load we used was hot but not overly hot, and none of the cases showed excessive signs of over-pressure in any of the rifles. I heard if a load is too hot it would cause vertical stringing, but why are these stringing horizontally?

I heard Horizontal stringing is caused by:

1) bedding issues (need a better bed for your rifle), inconsistent barrel harmonics causing rounds to spread:
Again I don't think it's bedding, my friends rifle is a stock Remi 700, my other friends is a 700 in AICS, and mine is a Savage McMillan that was professionally bedded. The stock Remi Rifle I can understand, but my rifle and my friends AICS are proven performers. Also as soon as we changed from that particular load the horizontal stringing disappeared altogether.

2) wind, can cause bullets to string:
Probably not the case here either. The horizontal stringing was consistent no matter the rifle, and I want to reiterate that when we switched from this particular load, the horizontal stringing disappeared for all rifles.

3) poor sandbag/bipod/prone technique -
Again this is not the issue as why would our "poor technique" only show up for this one particular load?

4) hot rounds causes barrel to warp and groups to spread -
alright this one might be it, but why would it be almost perfectly horizontal from rifle to rifle? If it is truly barrel warping, why are all 3 rifles warping in the same direction? ???

Only variable we found different between all the loads used that day was the stringing groups used Winchester Primers for it's loads. Can A Primer cause horizontal stringing? and why would it be almost horizontal from rifle to rifle?


PS: and FYI, here is a great (because it's short and simple) article I found on Vertical Stringing:
http://www.6mmbr.com/verticaltips.html

PSS: and FYI, diagonal stringing is almost always a scope mounting issue. Something is coming loose, either the mount or the rings.

EDIT TO CLARIFY: THIS ONLY OCCURRED FOR ONE PARTICULAR LOAD OUT OF 3 DIFFERENT RIFLES: I forgot the powder charge, but I know it was Varget, Winchester Primers, and 155gr Lapua bullets.

[Jack A Sol]

could the target have been moving at all?

[EricCartmann]

could the target have been moving at all?

I don't think so, we were shooting at different times. I am going to chalk this one up as a strange event that probably won't happen again.

[SDDuc996]

So it occurred with one load in all three rifles, but went away with another load?

[DSM]

Spin drift.

[EricCartmann]

So it occurred with one load in all three rifles, but went away with another load?

Yeah, a friend thought he nailed a load of 155gr Scenars so he made 100 of them. At first he thought it was the wind, but no one else was getting the same pattern. Then he thought it was just him, then I tried the same load in his rifle got the same result, so we just thought it was his gun that did not like that load, then I tried it on my gun same result. Then another friend who was just learning and setting up his Remi, tried it in his own gun and same results. ???

We know it's the particular load, but we are just curious to why it would all produce the same result between different guns and different shooter.

[EricCartmann]

Spin drift.

Wow! Just looked it and that is the only reasonable explanation. And as the barrel get's hotter (because of the hot loads), the more drift it creates. Kind of like vertical stringing but only it's horizontal because of "spin drift" due to the combination of bullet, wind, and hot load.

Thanks!!! Now I have at least a half way decent answer for what might be going on.

[EricCartmann]

Here is what I found on spin drift (aka the magnus effect): http://en.wikipedia.org/wiki/Magnus_effect

[SS.Pic]

While I think that would explain the vertical string. I don't think that's it here,but you maybe on the right track. Sure is weird tho.

[EricCartmann]

While I think that would explain the vertical string. I don't think that's it here,but you maybe on the right track. Sure is weird tho.

I think it does, because the rounds are naturally drifting due to the wind and the magnus effect. Even the first round has a drift, but as you put more rounds down range, the barrel heats up causing greater pressure and faster rounds increasing the magnus effect.