As with any manufacturer they use a blended powder for factory ammo. Norma does have load data available.
https://www.norma-ammunition.com/en-gb/reloading-data/300-winchester-short-magnum
Once I time a 2pc brake I red loc-tite the jamb nut. After it is cured I wrap teflon tape on the barrel threads to keep the brake from loosening. I use a new piece of tape after cleaning the barrel before reinstalling the brake.
You’ll have plenty of time to gather up parts as I learned last year with PT&G. They have great prices on the Wby 307 builder action , but plan on waiting. I was thinking on ordering a Vanguard barreled action in 257 Roberts , just couldn’t do it.
I hope you can receive yours in a timely manner.
I use the Tipton vise for mounting scopes with no problems. I also use the Wheeler Leveling System.
https://www.wheelertools.com/scope-mounting/mounting-tools/professional-reticle-leveling-system/119050.html?srsltid=AfmBOorddyOqzA9Yjs2OCwcoUEsPkUGvvq-UcQFoDhq9nk81rBautAiK
You’ll be shaking the frost out of the ground with Big Girl😁
I’ve stocked up on these for when I get my 378 back , price is decent for CEBs.
https://bulletcentral.com/cutting-edge-bullets-mtac-375-352-max/