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Made it out this am to validate at distance, was excited to see some results from 4-800 yards. Long story short, I am back to the drawing board for loads. The first time out I shot groups at 100 and 200 and had decent accuracy, probably 5/8 MOA. Not the tightest groups I have shot, but not terrible either. This morning was cold, but almost no wind, which is nice. My 100 yard zero groups weren't great, and things just got worse from there.
28 Sherman Magnum or PRC if you will
What jump were you using? A 2 shot per jump ladder would be the way to go first.
For hunting purposes you don't need 5 shot groups. In the hunting situation THE most important shot is the cold bore shot. The object is one shot, one kill. Two shot groups are the most relevant. If your cold bore shot and the follow up shot are within 1/2" of each other and your first shot hit the point of aim then you are good. 5 shot groups add other variables such as barrel creep with heating. Many hunting rifles have thinner barrels to save weight, which increases vibration amplitude of the barrel and faster heating because the heat capacity of the barrel is low, as is the stiffness. This makes it harder to shoot tight groups with more than 2 shots. I use a 20" long 0.9" muzzle .308 Win which is very stiff, vibrates at a low amplitude and is long enough to generate 2950 fps with a 150 gr BD2 bullet with a G1 BC equivalent to the 185 Berger Juggernaut and better penetration at virtually all distances. Weight is about 9.5 lbs, light enough to carry all day, but heavy enough to absorb recoil which can further be mitigated by a short suppressor or muzzle brake.
That was the issue, usually my outliers were the cold bore shots. Some where 1.5-2 MOA out from the center of the group.
I shoot an 18" Proof Sendero. All my hunting rifles have Proof Sendero contours, the longest barrel I have on a hunting rifle is 22" the rest are 20". Part of the reason I shoot those barrels is I notice very little, if any, POI change from suppressed to unsuppressed, amongst other things. Whatever the formula is, it seems to work. Conversely, my competition guns have 24" "competition contour" barrels and are like truck axles. I have virtually the same performance. Those guns I shoot 10 shot groups with, both zeroing and at distance. This emulates some of the matches I shoot that have long, 10-12 shot strings over a relatively short time frame. Once I find a load that works and will group well, I typically shoot a dot drill when I practice to avoid getting "group anxiety". I shoot MOA dots out to around 600, If I am around center of target, that is a win.
My "other" load is a mono. Those are the ones I actually couldn't find a load that wouldn't shoot. Easily the most forgiving bullet I have ever shot, more so than the berger hybrid even. The only issue I have with those is the low BC. I really could care less about the elevation, but they aren't real forgiving in the wind, which is the most important benefit of a high BC bullet.
That is crazy to me that such a small difference in seating depth change could make such a big difference. You could rack up a hell of a component bill running such minute adjustments. I would probably need to invest in a better set of calipers...
.105" jump to .115" jump. Mag feeding in my 300wm with the 205gr sbd2's
There are two generalizations you can make about monos vs C&C. The latter are much softer and don't penetrate as well at high speed impacts. Monos (all copper) bullets are etched by rifling where C&Cs "squeeze into the rifling. Our bullets generally will need a jump between 0.020-0.30". They shoot 1/2 MOA right off the bat in the 6.8 Western that has tight clearances in the lead/ free bore portion of the throat. Typically from my guns I can get sub-MOA groups at those jumps. If not then I do 2 shot jump ladders at 0.010" increments starting 0.005" off the lands. I have one Proof carbon barrel in a 308 Win with a short throat that gives me more trouble than the other barrels though.
