I'm research the 300 PRC and wondering if anyone has had any experience with thar round along with bullet weight, powders twist of barrel etc.
Have one, like it for what it is. Love it's slightly larger cousin 30 Sherman, aka the 300 PRC Improved. I'm taking the 308 caliber to the extreme end of reason with a 30-338 Lapua Improved and a 30XC, yet each of those don't hold a candle to what a 338 Lapua or 338 Norma or 338 Edge will do with half the effort.
It's just flat impossible to understate the inherent advantages of a 300gn 338 at distance. I would go so far as to recommend a factory Savage 338 over a custom 300 PRC, because the exterior ballistics tilt so heavily towards 338.
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To directly answer the questions:
300 PRC I would do a 9 twist to start with and shoot 208-230gn Bergers. I have 6, 8, and 9 twists in the big 30 cals, it's entirely bullet-dependent once you go faster than 9 IMO. The 6 will twist a cup and core in half, yet the 8 won't stabilize the biggest monos. Barrels twists are purpose-selected from the start for what they'll shoot. 9 will get you going and run a pretty wide variety of bullets. But NOT the heaviest because there's pretty much just one - the Berger 245. The heavy 308 cal SMKs are meh to me, I'd rather run a lighter VLD.
Powders, start with H1000. It's easy and forgiving, but not the fastest. From there move on to Retumbo, IMR 7828 SSC, VV565/568. H1000 is normally the easy button for tuning a load to group, and if you're shooting a 300 PRC out past a mile you'll need the grouping more than speed. So what if you go transonic 50 yards sooner, once you're in it you're in it and the only way out is through.