I'm soon planning to embark on my next XP-100 build. Currently planning to do a 30 cal cartridge that hopefully will push a 210-212-215 class bullet to at least 2750, maybe even 2800+ FPS (be nice to achieve 2850fps, just not sure I can get there with a barrel length of ~18"). I have not yet decided which case/cartridge. I will likely do a 30 Nosler, 30-28 Nosler or a similar cartridge. Maybe even a true wildcat, if I decide I need more case capacity. One thing I'm kinda hung up on is twist rate. I originally planned to do a 1:10" twist, but now am considering doing a 1:9" twist. The Berger twist calculator shows that a 10" twist would be adequate, but I'm still considering doing a 1:9" twist. Partly due to the lower expected velocity that my XP-100 will generate compared to a rifle length barrel with same/similar cartridge. I don't really have any plans to shoot the heavier 230+ bullets since I'm primarily going to use this gun for hunting. Maybe the occasional long range target, but still likely with 210-212-215 class bullets. Anyone here ever did something similar?