Is lateral "stringing" only caused by poor technique?

[copterdrvr]

Started working up some loads for a new JP medium contour .308 barrel/low mass bolt I just built up.

I had a couple of loads that gave me almost no vertical dispersion but kinda "stacked" five rounds horizontally at 100 yards. Winds less than 7 knots.

My question is:

a. does vertical stacking always mean that round is not in the node?
b. is horizontal "stacking" always an indication of poor trigger technique/followthrough?

Thanks for the replies!

 

[flashhole]

Don't know that I can answer your questions but I want to follow this thread.

With the Dan Newberry method, when seeking the Optimal Charge Weight you look for patterns with the lowest vertical spread at a specific powder charge. That would insinuate wind drift (horizonal dispersion) is not a consideration when looking for a good node. I have found this to be true with my rifles during load development providing I use a good solid rest.

My experience with horizontal stringing on calm days is usually caused by barrel heating. Again, with a good solid rest. Vertical stringing is shooting technique, at least for me.

I think you have opened Pandora's Box. I'm interested to see the replies.

 

[darth_ritis]

Hmmm, interesting topic ...

I've been thinking that vertical stringing is usually velocity differences, and horizontal is usually wind related. But human error could cause either one, as could a loose scope or stock or bipod.

Looking forward to what the more experienced guys have to say.

 

[CharlieNC]

Rifle and shooter problems certainly cause both vertical and horizontal stringing. But as you do OCW-ladder trials you can often observe consistent horizontal patterns in addition to the vertical nodes. This suggests to me that similar barrel harmonics are occuring in both planes. Why would one expect this behavior in only the vertical?

 

[Hondo64d]

Absolutely! I have never understood why a bunch of folks seem to think that harmonics affects only the vertical plane. is there some physics law I am un aware of that says a barrel can only oscillate up and down and not side to side, or a combination of the two?

Happy Independence Day to everyone! Let us not forget the things that caused us to declare our independence…

John

 

[djskit]

I have only anecdotal evidence, but I believe that horizontal stringing is primarily a marksmanship issue. While vertical can be either marksmanship or load node/loading technique.

 

[Smithcollector]

I've always thought that vertical stringing was the result of velocity variation, and that the node was the point where variances in pressure from burning powder caused a minimal variance in velocity.

 

[Fred_C_Dobbs]

...a. does vertical stacking always mean that round is not in the node?
b. is horizontal "stacking" always an indication of poor trigger technique/followthrough?...

No to both. Not always. Just mostly always.

 

[former naval person]

As Hondo says.

 

[VoxPatriam]

Absolutely! I have never understood why a bunch of folks seem to think that harmonics affects only the vertical plane. is there some physics law I am un aware of that says a barrel can only oscillate up and down and not side to side, or a combination of the two?

Happy Independence Day to everyone! Let us not forget the things that caused us to declare our independence…

Wouldn't a barrel be more prone to vertical oscillation just because of how it's supported in the stock though? Would a bad lateral gouge in the crown (especially on a longer barrel with a higher velocity round) contribute to a horizontal oscillation? I really have no idea and would like to learn what actually causes a barrel to flex in a particular direction.

 

[Twoboxer]

Absolutely! I have never understood why a bunch of folks seem to think that harmonics affects only the vertical plane. is there some physics law I am un aware of that says a barrel can only oscillate up and down and not side to side, or a combination of the two?

Happy Independence Day to everyone! Let us not forget the things that caused us to declare our independence…

Wouldn't a barrel be more prone to vertical oscillation just because of how it's supported in the stock though? Would a bad lateral gouge in the crown (especially on a longer barrel with a higher velocity round) contribute to a horizontal oscillation? I really have no idea and would like to learn what actually causes a barrel to flex in a particular direction.

From reading those who have actually studied this topic and developed OBT and OCW, part of the harmonics issue is thought to be a change in the size of the barrel crown. Further, many rifles do not have any part of the barrel supported by the stock.

My personal belief is that vertical strings can be caused by velocity changes, barrel heat, barrel harmonics and probably more (in addition to the shooter, mounting technique, bipod/sandbag, etc lol). But at 100yds, a 100 FPS change accounts for perhaps 0.2" change in POI (168gr, 2700fps and 2800fps, each zeroed at 200 yards, difference in POI measured at 100 yards).

Add wind to the list for horizontal stringing.

 

[VoxPatriam]

I'm with you on the vertical stringing. Granted my experience is mostly with service rifles up to 500m, but let's take shooter error off the table for a minute. We eliminate everything. NPOA, scope shadow, trigger control, etc. We're all human and stuff happens. That said what mechanical factors would cause horizontal stringing? Drifting scope reticle, wind, bad crown...?

 

[copterdrvr]

These are three of the targets from the last outing with the new stuff.

I get the vertical potential of not being in a node as the velocity is going up but I never thought about a node being anything but vertical. That's why the lateral one had me confused-but from what some here have said, I guess it's possible. I always only assumed vertical because of the orientation of barrels/actions and I can't remember the recoil of a gun pulling the barrel sideways-without some kind of comp action, anyway!

 

[flashhole]

Something I found on the net. Didn't find a similar "article" on horizontal stringing but lots of shooting forum discussions come up when you do a search.

CURES for VERTICAL STRINGING

 

[Drifter™]

After an OCW and / or ladder test to find a charge weight, experiment with bullet seating depth. One method is to load some ammo long (or as long as your mag and chamber will allow), then take a seating die (preferably with micro-type adjustments) in a hand press to the range. Adjust shorter in ~0.005" increments and see what happens to your group size and shape.

I suppose this borrows from the OBT concept: Optimal Barrel Time Paper

 

[HodgdonExtreme]

Remember how the antennas on car use to be a long thin metal rod?

Ever bend one over, let it go and watch it whip around (in a standing wave harmonic)?

Ever notice the antenna tip wanders around in a circular motion?

That's because the harmonic is not occurring in just one plane.

There is no reason to expect your barrel to only whip up and down.

 

[copterdrvr]

Roger that!

The targets show the progression working up to an acceptable load to start "fine tuning". The thing that caught my attention was the lateral spread to a vertical spread to a more or less rounded group with all rounds loaded exactly the same except for a powder range difference of .6 grains of 4064.

I always start with powder first and then play with seating depth-unfortunately I don't have any room to play with to insure they'll fit in the mag...

I like the antenna analogy-that makes sense!!!! ;-)

 

[HodgdonExtreme]

Remember how the antennas on car use to be a long thin metal rod?

Ever bend one over, let it go and watch it whip around (in a standing wave harmonic)?

Ever notice the antenna tip wanders around in a circular motion?

That's because the harmonic is not occurring in just one plane.

There is no reason to expect your barrel to only whip up and down.

I should add the vertical antenna doesn't have gravity acting on it, causing it to droop "cantilevered beam" style like a barrel.

This is why the vertical component of barrel whip/harmonics is more pronounced than the horizontal.

 

[copterdrvr]

. One method is to load some ammo long (or as long as your mag and chamber will allow), then take a seating die (preferably with micro-type adjustments) in a hand press to the range. Adjust shorter in ~0.005" increments and see what happens to your group size and shape.

I've loaded for bolt guns for a while and put together some killer loads for my AR15's but the 308 AR is new for me. Have you had many situations where the best load was less than the 2.8 inch mag length limit in a 308 AR?

 

[Drifter™]

I've loaded for bolt guns for a while and put together some killer loads for my AR15's but the 308 AR is new for me. Have you had many situations where the best load was less than the 2.8 inch mag length limit in a 308 AR?

Haven't loaded 308, but with a 6.5 Creedmoor AR, absolutely.