I ran 8 powders and 2 bullets through my new custom 204 last fall. The best combination was 10x and the 39 SBK. Every gun is different. My group was good enough to quit load development.
Powders tried
10x, 748, 335, 4895, Benchmark, Varget, 322, 2230
Bullets
39 Sierra Blitzking
40 Hornady V-Max