Horizontal Stringing

[williada]

This is the last of my contributions, hopefully others will share their experiences and not withhold information. Ultimately the gear will be the same then once again success can be measured by skill of reading wind, mirage and light.

[DenisA]

Went down to 100y today to check 300wsm speeds. Tested groups started as a horizontal string, across an antimode to a vert string. Funny that this result came about just as this thread was posted. Sorry David, I couldn't get to shoot your preferred distance.

[RAVEN]

Denis
David shoots at that distance for a reason I expect
if your using flat base well go right ahead all good

[DenisA]

Denis
David shoots at that distance for a reason I expect
if your using flat base well go right ahead all good

I'm not using flat base.

[Brad Y]

So Denis what load are you going to explore further here? Be good to hear what your thinking in light of the comments added.

[plumbs7]

Thanks Denis for posting ur groups, always interesting !

I have failed ! I was trying not to post anything on forums for at least a week or two! Can't help myself!

We seem to keep coming back to barrel harmonics and what they do . At 100m-140m it's quite clear in what is happing . Below are some groups shot at 97 m from a very clean Bart. I started a thread on a Facebook page of us locals saying to clean or not to clean? Where I was saying that my Bart took 6 shots to start coming on song!


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The next afternoon I set out to prove this but later had to retract my previous statement as after 3 shots it was on .
Even with a big donger ( barrel weight) on the end the first few shots seem to throw out to the left and a little low! Was always blaming myself being a cold shooter ! But the pattern seems to keep appearing!

I'll try and decipher the above ! Shot 1 is actually shot 2 . Shot 1 from a shiny clean barrel was 2763 from memory but print perfect elevation but left of normal poi.
Then you will see a shot left in the lower group and a shot hi as the barrel fowls and the vibrations from the rounds going down a clean bore lessen. Then the group is deadset on for 6 shots and would have been for 7 shots (shot 10) . But I chambered the round and cooked it . Tried to unchamber the round and dropped a few grains ( or more) in the breech. I cleaned out the breech seated the pill and chambered then fired fora a on line shot but low. That last shot low proves to me that I've got the harmonics right in this Rilfe as even with a huge velocity drop ( sorry didn't record what it was) it was on line but low . So can harmonics throw a round sideways ? Well it seems it can !


The above is 6 shots ( from memory) 168gr Bergers fireforming loads . See the pattern first shot out to the left , in this case low too at 2690 fps .

But can it throw a round into a magpie ? I think it was a bit more than harmonics , maybe wind , some lose scope mounts and the wind . Who knows!

[DenisA]

So Denis what load are you going to explore further here? Be good to hear what your thinking in light of the comments added.

Brad, the M.E limits for 185 gn is 2920 so I have to stay with the lower charge. I'll shoot 64.0gn on Saturday at 900m but I'll explore the complete length and shape of that 64.0 gn node in the coming weeks. I have a feeling this barrel may have settled in its speed finally.

I should add, it was extremely windy at Belmont today with patchy cloud constantly throwing shade over the targets too. 25 - 40 km/h winds, constant gusts and swirling from all different directions. I know it doesn't make too much of a difference at 100y, but it does a little and it was clear to see the reticule move off the POA as the wind gusted and light levels dropped on and off. I took my time, never let the barrel get hot and was as opportunistic as I could be. I was pretty happy with the results considering the terrible day for testing. I had to get the speeds sussed prior to the weekend.

[Longranger]

Just wondering if people using adjustable tuners have a different setting for each range?

Why? Wouldn't the tightest group allied with a low ES and SD work at all ranges?

[johnk]

It can happen, but not with the heavier tuners, it would seem.

[DenisA]

Just wondering if people using adjustable tuners have a different setting for each range?

Why? Wouldn't the tightest group allied with a low ES and SD work at all ranges?

I'm far from an expert, but from what I've learnt from here, the answers no, not when your talking extreme accuracy because.....

1. Maintaining an ES of 0 is impossible
2. When you tune a tight group at a certain distance, you've found an area where all of those slightly different trajectories intersect closest together at that given distance. As you move the target forward or backward of that point of intersection your moving the target in to areas where the trajectories are further spread from each other.
3. Different launch angles (angle of the bore line to the target, height of target above the mound) changes the intersecting point of the trajectories with the same load. Imagine 2 garden hoses abreast. The top hose with a lower pressure and the bottom with a higher pressure. Now change the angle up and down and watch the point that the 2 streams of water intersect change.
4. Atmospheric influences have parabolic effects on bullets that are constantly shedding speed and BC.
5. Barrel harmonics and positive compensation can be used to reduce the effect of MV variation by causing slower shots to be thrown higher to intersect with faster shots that have been thrown lower at any given distance.
6. A tuner can allow you to adjust the positive compensation without changing the load at any given distance.

[RDavies]

Just wondering if people using adjustable tuners have a different setting for each range?

Why? Wouldn't the tightest group allied with a low ES and SD work at all ranges?

I'm far from an expert, but from what I've learnt from here, the answers no, not when your talking extreme accuracy because.....

1. Maintaining an ES of 0 is impossible
2. When you tune a tight group at a certain distance, you've found an area where all of those slightly different trajectories intersect closest together at that given distance. As you move the target forward or backward of that point of intersection your moving the target in to areas where the trajectories are further spread from each other.
3. Different launch angles (angle of the bore line to the target, height of target above the mound) changes the intersecting point of the trajectories with the same load. Imagine 2 garden hoses abreast. The top hose with a lower pressure and the bottom with a higher pressure. Now change the angle up and down and watch the point that the 2 streams of water intersect change.
4. Atmospheric influences have parabolic effects on bullets that are constantly shedding speed and BC.
5. Barrel harmonics and positive compensation can be used to reduce the effect of MV variation by causing slower shots to be thrown higher to intersect with faster shots that have been thrown lower at any given distance.
6. A tuner can allow you to adjust the positive compensation without changing the load at any given distance.

BUT, a very low ES will make it more consistent at varying ranges, as in not as much change required to keep it accurate from 500 to 1000yds. Though you will still need to get it in tune, a low ES (less than 15 fps) is certainly something to work towards at 1000yds.
That said, I shot my tightest ever 600yd group last week with my new barrel. When I cronied it, I found a 50 fps spread (going through the erratic hump stage) . This load might have worked at 600yds but I wouldn't want to use it at varying ranges or 1000yds. A primer change has brought the ES down to 12, so there is hope for this barrel yet.

[Steve N]

Denis that photo through the scope is incredible.
Steve

[Tim N]

My question about different settings came from the different recommendations on which way to move the tuner depending on distance.
So I'm thinking some shooters might have scope settings and tuner settings for all distances?

[ecomeat]

Denis, did you shoot the 100 yard groups Round Robin, to average it out ?

[williada]

Tim, I feel I have to say briefly it depends on your muzzle angle, torque and barrel harmonic length. Scroll down through the link http://www.varmintal.com/amode.htm