I just loaded more rounds for load testing so I have a box of them now and no splits yet with brand new Winchester 300 WSM brass, no annealing. I imagine if you can find 325 brass it would be better yet. I mentioned in another post I use 2 tapered expander buttons from Redding Dies to get me there, 0.308" - 0.358" and 0.358" - 0.416", lubing inside the neck with Q-tip.I’m wondering on your 416 WSM what cartridge u used to size up. 325 is what I’m planning on using. There are subtle differences in case dimensions with 7mm the longest to shoulder followed by 325, and then 300 and 270. I’m leaning toward using the 325 but reaming the chamber to 7mm WSM shoulder length and hopefully gain a few fps.
Also do you have to anneal your brass? Thanx for the info. I’ll post some pics of my project as I go.
Silky