What do you do for Horizontal Dispersion?

[miningshawn]

Here is the scenario. You have come up with a great load that shows no vertical dispersion, has very low ES and SD, but has an annoying 3-4 bullet widths of horizontal.

What steps would you take? Seating depth, neck tension, loading technique, barrel tuner, other?

I am curious to see what comes out of this - I am sure that most of us have encountered this but I haven't found a thread dedicated to it. No wrong answers.

 

[screaminweasil]

Rear Bag/ Front Rest setup.........don't want too stiff a rear bag or front rest pad. Wind Flags..........

Assuming you can shoot sub MOA groups consistently..............

Last to play with is seating depth

 

[MikeMcCasland]

No wrong answer, but no easy answer. Also, I've written this three times over, and I keep coming across like an a-hole; I promise that's not my intent. I want to contribute, I'm a genuinely nice guy, it's just late and I'm inarticulate...but here it goes...

Answering this from an F-Class perspective; if we're talking hunting guns etc. that's a different story. Also operating on the assumption that you don't want answers to include range conditions/wind as a contributing factor.

That said, I think I know the answers you're looking for, but I also think the scenario is a bit flawed. I don't see that there's enough info to give a full & complete answer. For example, 3-4 bullet diameters wide at 100 yards is a non-starter; at 400 and beyond it's probably something you could work with. Need to know what caliber we're talking about too.

First, the person in this scenario never had a "great load" to begin with. They had a load with flat vertical and good chronograph numbers, but that was all it ever was. To call it a "good load" would imply it was grouping well, and doing it with relative consistency (sounds like it wasn't).

If it ever shot well, I'd be looking at tuner (assuming it's equipped, because that's easiest to test), depth, and then tension (in that order). If those failed, I'd be going back to the last point where I had confidence and working from there.

The scenario also kind of paints you into a corner. Is the gun throated for this bullet and you have 3,000 of them just for this barrel? An "it's going to work" type thing? How many powders were tried before settling on this one? How many primers? I usually don't find myself in the scenario described because I try to cast a wide net very early by testing 2-5 powders and 2x primers during the first 100 rounds; it usually becomes really obvious what combo is going to work well. I suspect that eliminates 90% of what is described in the scenario.

I would also perceive the chronograph data as irrelevant (outside of knowing if you're going 2000fps or 2800fps) until you get your mean radius relatively tight, and a consistent POI. Once you've got those two things, I think that's when you can actually start to tweak a load to make it accurate.

In summary, I probably wouldn't find myself in this situation, because the person in the scenario is backed into a corner, trying to force a combo to work. If I did find myself in that scenario I'd have a new barrel spun up if I couldn't sort it out really quickly, because components are way more costly (and now significantly more rare) than a $600-800 barrel job.

Signed,
Not a-hole Mike

 

[miningshawn]

No wrong answer, but no easy answer. Also, I've written this three times over, and I keep coming across like an a-hole; I promise that's not my intent. I want to contribute, I'm a genuinely nice guy, it's just late and I'm inarticulate...but here it goes...

Answering this from an F-Class perspective; if we're talking hunting guns etc. that's a different story. Also operating on the assumption that you don't want answers to include range conditions/wind as a contributing factor.

That said, I think I know the answers you're looking for, but I also think the scenario is a bit flawed. I don't see that there's enough info to give a full & complete answer. For example, 3-4 bullet diameters wide at 100 yards is a non-starter; at 400 and beyond it's probably something you could work with. Need to know what caliber we're talking about too.

First, the person in this scenario never had a "great load" to begin with. They had a load with flat vertical and good chronograph numbers, but that was all it ever was. To call it a "good load" would imply it was grouping well, and doing it with relative consistency (sounds like it wasn't).

If it ever shot well, I'd be looking at tuner (assuming it's equipped, because that's easiest to test), depth, and then tension (in that order). If those failed, I'd be going back to the last point where I had confidence and working from there.

The scenario also kind of paints you into a corner. Is the gun throated for this bullet and you have 3,000 of them just for this barrel? An "it's going to work" type thing? How many powders were tried before settling on this one? How many primers? I usually don't find myself in the scenario described because I try to cast a wide net very early by testing 2-5 powders and 2x primers during the first 100 rounds; it usually becomes really obvious what combo is going to work well. I suspect that eliminates 90% of what is described in the scenario.

I would also perceive the chronograph data as irrelevant (outside of knowing if you're going 2000fps or 2800fps) until you get your mean radius relatively tight, and a consistent POI. Once you've got those two things, I think that's when you can actually start to tweak a load to make it accurate.

In summary, I probably wouldn't find myself in this situation, because the person in the scenario is backed into a corner, trying to force a combo to work. If I did find myself in that scenario I'd have a new barrel spun up if I couldn't sort it out really quickly, because components are way more costly (and now significantly more rare) than a $600-800 barrel job.

Signed,
Not a-hole Mike

Good reply. I agree with most of what you have here. Here is a scenario:

You managed to score 1000 of anything - let's say Berger 130 hybrids - during the shortage. You have a sufficient supply of primers, good brass, suitable powders, and a barrel that should shoot well. After a full workup the best ES, SD, and vertical happen to have horizontal - and only horizontal - dispersion.

If I have it right - you say 1.) if it shoots well, try a tuner 2.) change components 3.) buy a barrel. Considering the market number 1 looks like the best option.

I wasn't trying to be deliberately vague. I am sincerely interested in how folks tune for horizontal stringing when it is the outlying parameter.

 

[Capt. Oblivious]

IMO the Internet taught to many people that ES is where its at, every time some one says to me "but I don't get it the ES is under so and so but the groups suck" I just ask them if they shoot a competition where the guy with the best score wins or the guy with the best ES.

At what distance are you seeing that 3-4 bullet horizontal ? If its at 100y that load is not the one to work with

 

[MikeMcCasland]

Good reply. I agree with most of what you have here. Here is a scenario:

You managed to score 1000 of anything - let's say Berger 130 hybrids - during the shortage. You have a sufficient supply of primers, good brass, suitable powders, and a barrel that should shoot well. After a full workup the best ES, SD, and vertical happen to have horizontal - and only horizontal - dispersion.

If I have it right - you say 1.) if it shoots well, try a tuner 2.) change components 3.) buy a barrel. Considering the market number 1 looks like the best option.

I wasn't trying to be deliberately vague. I am sincerely interested in how folks tune for horizontal stringing when it is the outlying parameter.

Just starting from the top..

I would disagree with placing a significant level of emphasis on the ES/SD. If you're using ES/SD as the primary metric to determine "is my load worked up"...that is very likely what's leading you astray (at least in my opinion; I'm often wrong). The target is telling you it's not in tune.

Low ES/SD is a byproduct of a good load, but it's been my experience that great shooting loads can't be easily identified by ES/SD (especially by shooting a statistically invalid numbers of shots to arrive at those numbers).

For example, you could take any 6BR variant and dump qty 5 charges of 29-31gr of H4895 in .2gr increments behind any 90+gr bullet in Bergers portfolio. Because of that cartridge, that powder, and that bullet, the numbers on the chronograph are inherently going to be very low (pretty much everything will be sub 5fps SD/sub 20fps ES). If you happen to just park it at the lowest ES/SD of the day, and go work depth, you're very likely not in tune.

The only "works 100% of the time" way I've found is to look for vertical POI on target (usually at ~300+, but can be done closer). Once you've found a charge range that impacts in the same general area, go work depth.

There are guys who claim they can go shoot 50 rounds across a chronograph and find their powder node; I don't believe them to be lying either. I can definitively tell you though that it hasn't worked consistently for me. In fact, it's led me astray more often than not....even when I'm trying it on a known combo (i.e. 8th barrel cut off the same reamer, same powder/bullet/primer/case as the last). I would love nothing more than for someone to show me how to make it work, because it'd make life a TON easier.

Moving on...

I wouldn't pay to have a tuner installed if you didn't have one on there already. There's a chance you could fix it with a tuner, but I wouldn't bet a $100 threading job and a $200 tuner on it.

Based on your response, my best advice would be to go re-shoot your powder node, but this time leave the chronograph at home and let the target tell you. If you do that, I bet you wind up at a different powder charge.

Theoretical vs. actual...

 

[flintcreek6412]

If you are basing your great load statement off being in a nice wide node over many charges and not simply one charge that shows no vertical I would use seating depth to find what works best. IMO, seating depth and tuner do about the same thing. I have never cared about ES/SD. I only care what's on paper.

Sometimes a bullet/powder combo just don't work. And having a great vertical node is really hard to not want to MAKE work. But sometimes you just have to pass on it and try something else. If it's a known load like say 43-44 gr Varget and 200-20x and you can't make it work it's simply new barrel time. I've got a barrel with 100 rounds on it sitting on the shelf because it didn't shoot for squat. That's a hard pill to swallow sometimes.

I will say that once I was baffled and frustrated with a similar situation. For the hell of it I simply changed from CCI BRs to FGMM primers and it turned into the best load/barrel combo I've ever owned. I don't know how it changed it, but it did so I didn't question it.

 

[CharlieNC]

I recall reading Tony Boyer's book regarding load development. While the exact details may be off, the principle is what's important. He loaded 2 each for a full matrix of 8 charge weights x 8 seating depths = 64 different load combinations. Choose the best load based on size and shape, but I don't recall if he favored a little vertical vs horizontal. But pure heresy, shoot it in a normal wind instead of calm to find the best wind bucking load.

 

[rardoin]

Evaluate the rest set-up as mentioned. Perhaps shoot a test with a different rear bag and see if you still get the same pattern. If so, play with seating depth. I would use a tuner only to keep the load in tune once you dial it in.

 

[JEFFPPC]

A record holding short range shooter told me he favors a bit of vertical in a load as he feels it helps fight the wind. From a mid to long range perspective that is not what most people want to see, including me. I have found groups that shoot both small and round have worked best for me. I have found if you developed your load by using the tuner, your on a knife edge. Develope the load , use the tuner to keep it there over rounds fired. I have had luck with some barrels when I could not get the shape group I want, do so by increase in neck tension. I have often thought about developing a load by not shooting groups but by shooting 1/8 dots. Basically that's what we do at any type of score match. I have a new 6PPC barrel coming.....just might experiment. So load #1 shots all the time in the high zeros to mid ones while load # 2 shoots low to upper ones. But, load 2 averages one more dot every time the 2 loads are fired. Which one would you use. Shape of group would certainly be in play.

 

[Coyotefurharvester]

If you shoot the rifle rested on it's side and the group is vertical, you know it's not the shooter.lol.

 

[GLShooter]

I'm no world beater but seating depth adjustment would be my fix.

Greg

 

[Nature Boy]

I added sand the the ears of my rear bag. Cut my horizontal dispersion by 1/2

 

[mikecr]

Assuming you had completed full seating testing before powder development, I would now fine tune seating (within it's window) for tightest group shaping.

 

[PigButtons]

If you shoot the rifle rested on it's side and the group is vertical, you know it's not the shooter.lol.

Or? If the shooter lays on his side and the group is diagonal you know it's not the wind. Lol

 

[Homerange]

Only struck this once with a newly acquired 7mm08 and it was loose action screws.

 

[garandman]

I added sand the the ears of my rear bag. Cut my horizontal dispersion by 1/2

Along the same lines...Im guessing not being aligned up properly behind the rifle could kick the butt left or right, and hits right or left...

 

[Knotwild]

I had a rifle give me a flat straight horizontal line with 5 shot groups. On a whim, I seated them incrementaly deeper in the case. The horizontal dispersion disappeared. It wound up being about a half inch gun.

It's a simple thing to try and you'll know immediately if that's your answer - so not much wasted time.