Tuning above the area of maximal wind sensitivity at 1K.

[seymour fish]

Have found a repeatable phenomenon ladder testing at 1K with positive compensation proven F/tr setup. On finding a load that shoots a perfectly flat waterline yet with tremendous width (presumably wind sensitivity, but....?), the next incremental powder charge up, a tenth of a grain, produces the smallest group. Another tenth, and group moves up 3-4" and opens 50 percent. Additional tenth, and she moves up another 3-4" and group size opens a similar increment, to end at perhaps 4-1/2 to5". Has anyone else seen anything similar ? Could the explanation lie with marginal gyroscopic stability of 1.3 ? Your thoughts, please. Seymour

 

[CharlieNC]

Seymore all my load optimization is at 200yd and I also see repeatable horizontal patterns, which are of larger magnitude than the influence of the wind. And certainly not stability at this distance. As with vertical I have always attributed this to harmonics, and seek to tune the node for this as well.

 

[TAJ45]

Have found a repeatable phenomenon ladder testing at 1K with positive compensation proven F/tr setup. On finding a load that shoots a perfectly flat waterline yet with tremendous width (presumably wind sensitivity, but....?), the next incremental powder charge up, a tenth of a grain, produces the smallest group. Another tenth, and group moves up 3-4" and opens 50 percent. Additional tenth, and she moves up another 3-4" and group size opens a similar increment, to end at perhaps 4-1/2 to5". Has anyone else seen anything similar ? Could the explanation lie with marginal gyroscopic stability of 1.3 ? Your thoughts, please. Seymour

Seymore all my load optimization is at 200yd and I also see repeatable horizontal patterns, which are of larger magnitude than the influence of the wind. And certainly not stability at this distance. As with vertical I have always attributed this to harmonics, and seek to tune the node for this as well.

So far, I read much more than I shoot. My very first thought was bbl harmonics as suggested above. Your input of the low stabilization factor in conjunction really gives me pause for thought on how one could trigger or combine with the other to open groups further.

 

[seymour fish]

So far, I read much more than I shoot. My very first thought was bbl harmonics as suggested above. Your input of the low stabilization factor in conjunction really gives me pause for thought on how one could trigger or combine with the other to open groups further.

Charlie and TAJ, appreciate your thoughts. The flat waterline is typically 2 Mona width, then a tenth of a grain more and quarter-minute in optimum condition. Never heard of such. Doubt it's the med Palma. Something ragged edge somewhere

 

[JohnKielly]

I once watched a guy tune a barrel for a particular purpose using a muzzle tuner. he could repeatably get groups vertical & tease them into forming a regular pattern, then a tight group, then by continuing the adjustment, get them to finally string out horizontally.

I suspect that you have the latter situation.

 

[Alex Wheeler]

Load that flat powder charge, adjust seating depth to shape the group. Its pretty hard to tune a load to shoot totally flat at 1k without having horizontal in the group. Normally what seems to agg best is a 2-3" tall group with about a inch of width. You will bring it in with seating depth though, just go a couple thousandths at a time.

 

[TAJ45]

Load that flat powder charge, adjust seating depth to shape the group. Its pretty hard to tune a load to shoot totally flat at 1k without having horizontal in the group. Normally what seems to agg best is a 2-3" tall group with about a inch of width. You will bring it in with seating depth though, just go a couple thousandths at a time.

This sounds like advice from an intelligent, experienced shooter. I'm gonna need another 20 good years.
Not OP but thanks Alex.

 

[seymour fish]

Thanks John, Alex, and Tom. Exactly what I was looking for, and very kind of you. Seymour

 

[memilanuk]

As a general rule, you want to remove all the vertical you can with Powder and refine the shape with fine seating tweaks.

Where would neck tension fit into your tuning process?

 

[Northridge]

Load that flat powder charge, adjust seating depth to shape the group. Its pretty hard to tune a load to shoot totally flat at 1k without having horizontal in the group. Normally what seems to agg best is a 2-3" tall group with about a inch of width. You will bring it in with seating depth though, just go a couple thousandths at a time.

This is by far the best approach as Alex and Tom have stated. Not an exception to the rule but the most proven method to reach the best end result. In my experience neck tension affects my vertical dispersion and general grouping but typically will not eliminate horizontal dispersion. If your completely flat with vertical draw a few thousands out or keep drawing back till grouping go's round bingo your there and it will shoot conditions better. Neck tension also helps with the dropped shot phenomena....

Shawn williams

 

[TAJ45]

I usually end up having more solid agging loads with more tension than less. So I start off with medium-heavy and work out all rough powder and seating. Then I explore tension, Then I chase my tail and go back to fine powder and fine seating.

Tom

All of this should at least be in a sticky if not published.....!! I luv it.

 

[seymour fish]

I usually end up having more solid agging loads with more tension than less. So I start off with medium-heavy and work out all rough powder and seating. Then I explore tension, Then I chase my tail and go back to fine powder and fine seating.

Tom

Tom, would you consider 2 thou press fit medium-heavy ?

 

[seymour fish]

Where would neck tension fit into your tuning process?

And does a hard jam take neck tension largely out of play as a tuning tweak?

 

[memilanuk]

Depends on the situation, caliber, bullets (pressure ring vs not). My dasher stuff I start about 3ish if the bullets have a mild or non distinct pressure ring. The bullets I was using the last couple of years and at Nationals have very dominant pressure rings, and I was a tad over 5 thousands...... And not annealing to boot!

Sweet jesus. I normally run a .308 @ around 2 thou neck tension i.e. .306 ID for the neck, with bullets from a yellow box (never measured for pressure ring). Less than i.e. 1 thou, etc. and I worry about the seating depth getting bumped around in transit.

What does 3 to 5 thou neck tension look like in terms of pounds force on a seating force gauge i.e. K&M or hydro-seater?

In my limited experience - primarily .308, with some .223 and a bit of 6 BR/Dasher long ago... anything over 2 thou neck tension was borderline unusable with an arbor press - as in I was having to almost lean on that short little handle, completely over-riding any 'feel'.

What are you doing different that makes that much neck tension doable with an arbor press?

 

[dkhunt14]

Most Dasher guys are running .010 to .015 wall thickness so 4 or 5 thousandths tension isn't as much as others. As an example I run .0135 walls on my WSM and it isn't as much as when you use a smaller bushing on the Dasher. I am like Tom and run more tension then most, it seems to even things out at 1000 yards. Matt

 

[memilanuk]

With my .308s, I normally run between 11-12 thou (Winchester) to 14-15 thou (Lapua turned vs un-turned), so that isn't so different.

I saw a very interesting post on a FB group from a fellow (James Phillips, I think) where he was tuning a load for either 600 or 1000yds, can't recall which... as he went down in neck bushing size (increasing neck tension), the group size stayed roughly the same... but the ES/SD dropped dramatically. Granted, I think that might have been a .300WSM, so maybe not entirely apples-to-apples, but definitely something that piqued my curiosity! I know you guys don't care so much about ES/SD, but for others of us... its very much an area of extreme interest.