My 308 Win has a 1:12 twist and shoots 208 A-max and Berger 210 VLD just fine.
With the added velocity of the 300 WM I believe you will be just fine with the 200gr.
I took Barnes BL-C2 data and worked up 1gr charges with both primers to see where I hit pressure. No load work up intended , just finding max pressure for given powder.
Today ran a comparison between Fed 215 and CCI BR-2 primers in my boys 30-06 in a Rem 783. I decided to compare my Magnetospeed and Gramin. The Garmin did miss the Fed 215 at 59 grs. The MS was always showed a bit more velocity. As far as the 2 primers the Fed 215 started to show some flattening...
Second bullet I tested today was in the 340 Wby was a flop. Took 3 tries to catch the base. Ran out of jugs to test anymore bullets today. I started with a clean bore with these bullets HBN coated , no cold bore issues.
Kinda cool seeing the center undisturbed.
Did a little jug testing today with the 30-30. Took 2 attempts on this one. I was a little worried that the 30-30 would be too slow for good expansion , no issues to report. I’m happy with this load. I was set up at 30yds.