Horizontal IMO, as you mentioned, should be ruled out. That is lot of wind.
Verticle: I believe you are on the right track. However, in my experience powder amount is helpful but how far off the lands are you should be considered as well. My rifle shoots almost the exact same spot with 1 grain powder change. For example 56.5 and 57.6. 57 vertically strings the bullets. My rifle also likes .075 off the lands more than it did .050 for the same powder amount.
Perhaps you could load up some in the 44.6 to 44.9 with varying seating depths?
Thanks for the reply. My next test, depending on what input I got, was going to be Berger's recommended test. All those loads were .010 off the lands, debating, since I use the gun for hunting, to try touching the lands, or just use .010 off the lands as my longest OAL...that was 2.200 base to ogive as it stands
I am sure an expert will chime in but I think you are headed the right direction. My LR rifle has a long throat and with the bullets .015 off I did not have enough bullet in the neck. I had the same issue with a couple of other rifles too. My 3006 has a short throat and is solid at .010 off.
Anyway, I happen to believe that for hunting, a repeater, and possibly someone else shooting/handling my rifle it was best to pull the bullets back and seat them deeper. It worked for me. I like the fact it seems to be fine with .075 off right now and the bullets are not knocked off center easily.
Was certainly a little nippy this morn...I shot a couple of groups at home with a new lot of bergers and some new brass in a couple of my 260s...I had a gusty 2:00 wind at about 5-10 definitely will spread out your groups....Both were wearing a different scope so after the sighters a .53 & .56 were very respectable for me (the SDs were bad but expected with new brass)...They should only get better after the new brass gets a couple more firings and I fine tune the seating (new dies at Berger make a whole new bullet)...
Your charges seem to be in a good node...Normally if you get to your sweet node the groups won't change too much plus or minus a couple of tenths...When you start your seating tests stick with one charge in your case
average out your best 4 and it looks like 44.7 or 44.8....Did you happen to shoot these over the chrono?
After the first seating test you can narrow that down even more with a couple more seating tests....I generally try .010, .020, .030, .040 .050, .060, .070, .080 &. 090 the first time....The second time I take the two or three best ones
and go in .005 increments in each direction from them....
Once I find what seems to be the best seating then I go back to the charge and work both ways from there....If accuracy picks up at another charge then I once again work the seating .003 in both directions...Usually you will find a home for both but sometimes it takes a couple of trys....Better than random chasing your tail.
That wind combined with the cold made for some unplesent shooting over 29 rounds and about an hour of somewhat hurried shooting.
I used my chronograph (shooting Chrony F-1) when I did my initial testing, 44.8 grains (with a statistically insignificant 3-shot group) averaged 2941FPS with an ES of 29 and SD of 14.53. That was also the best 3-shot group of the day at .539MOA with a .385 vertical.
Today I had chrony issues, a bunch of errors, and velocity readings that had a range of 1500 FPS (got what I paid for with a free chrony)
I'm thinking, I'll go with 44.8 grains, because it's had the best overall results. I'll rough in my load going .010, .050, .090, .120 off the lands, like in the Berger manual, for now...my seater die does not have a micrometer, so the real fin adjustments are very difficult.
Got your PM, gonna get my self organized and get that mailed out.