I'm not getting the bit about the 204 fouling to the point you're loosing accuracy. I think its more with the rifle then the gun.
In a PD I go through several rounds, My 204 Ruger in Ruger #1 does't loose it. I use Benchmark and 32 gr. Hornady V-max.
I think I'd check the barrel of your rifle.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071