Interesting read so far. I just shot my 375 Ruger with 350 gr Rhino's. Got speeds from 2263 to 2279 fps - up and down - with our local powders (Somchem S365) Not ideal. Big variation in speed. So have to wait until they are online again. Will update when I find some speeds s355 or s 341. Will put the Ruger up there I think . Ruger Alaskan 20 "
16 fps extreme spread.
this would translate to about 5 or 6 fps std deviation.
that is extremely good for 10+ shots.
given that 100, 200, and 300 yd benchresters do not even worry about this, and palma shooters (800, 900, and 1000 yds) look for std deviations less than 10, you are doing pretty well.
added to which, the main factors that affect velocity variation do not include powder choice.
changing primers can help, as can charge wts.
other things include case case capacity consistency, neck thickness, and the temper of annealing in necks, which in part relate to neck tension consistency.
if you want to turn your necks and get seriously into annealing, weigh your brass etc, go for it.
you will have to batch your brass and keep it in those batches, all fired the same no of times.
oh, and you might have to jam your bullets 0.010" or thereabouts into the rifling.
is this good for hunting rifle reliability, and will they fit the mag?
nothing like opening the bolt on a loaded round, leaving the bullet stuck in the throat, and getting powder in your locking lug recesses out in the bush where you can't clean it out.
be happy with your load if it is at max SAFE pressure. it does not get much better than that in custom tight necked chambers, let alone factory ones.
the powder that gives the fastest speeds at the same pressure is what to look for, particularly in a calibre like 375.