300WM Brass, my experiences...
I really wish I had seen the brass question posts when they were posted.
FC brass tends to kinda suck from a consistency perspective.
Lapua is pretty great.
Norma brass is the best, and it used to be that the Lapua brass was made by Norma. YMMV.
Peterson is pretty good. I've loaded a bunch of their "Long" variant 300WM. That said, I'm a little unimpressed by the sorting of it (it seems to sort in 3 traunches of weight range, and if you sort them... you get ~8-10SD out of the loads.
In depth review of Peterson 300WM brasses:
Peterson 300 Win Mag brass - Standard Length vs. Long - Initial Data & Impressions Introduction This thread is being generated for a number of reasons, not the least of which is in relation to the comments and questions that have come up during the multiple active threads regarding the release...
www.longrangehunting.com
Hornady is ok, again, you end up sorting it.
Winchester is ok, still more need to sort it...
Remington is ok, still requires sorting....
Gunwerks brass is good, also required a fair amount of sorting...
Nosler brass is NOT USED. It's probably fine, but they sold me a boat load of 300WM brass years ago and the belts were out of tolerance on pretty much 40% of all of the cases. It was a debacle. Their basic attitude was that rather than replace all of the brass with a new lot (so that they were uniform), they'd send me individual pieces to replace the bad ones (of which there were many). As such, I avoid their brass like the plague.
ADG brass... I'd probably avoid it as I've had huge inconsistencies with some ammo loaded with it, and the massive swings in accuracy where related to the brass (weighed after the fact). That said, the ammo supplier is the issue as they clearly didn't sort... Of course, if you did that with Norma / Lapua / RWS / possibly Peterson, you'd be fine...
Quote from Long Range Hunting:
"I bought and received 800 cases of 300 Win Mag from ADG in April 2018. All but 15 pieces weighed between 247-250.9 grains. 3 were a little lighter (in the 246 grain range) and 12 were a little heavier (in the 251 grain range.) 369 of the cases were 248 grain, 231 cases were 249 grains, 117 were 247 grains, 68 were 250 grain. My water volume measurements of fired cases put them at 92 gr of water volume."
RWS is GREAT, like Norma and Lapua, but I did have to do a bit of sorting. It's also VERY heavy; don't try your normal load from Winchester / Remington / Hornady in RWS if that load is at the top of the range. (Same goes for Norma and Lapua brass, which tend to be heavier / thicker.)
Only Lapua and Norma are consistent enough that sorting is only required if you are SUPER anal (trying to get to that 5-10SD range.)