The 204 I believe is like the 17 with the respects that accuracy erodes quickly when copper fooled. I too shot silhouette in the 90’ s in raton. Our silhouette rifles mostly. Had cut rifling. Douglases were buttoned rifled, sure but they were also lapped. Our groves are much deeper and I think our bullets slower then the 204 cal.
So copper cleaning, idk if RB17 is still around, it was my favorite, Barnes makes a strong copper remover as does Sweets. Hoppes doesn’t clean very well and is kinda ok on powder fowling. If your an old time hoppes fan, I humbelly suggest there are other, better cleaners out there. Butches bore shine is milder then theaforementiond copper removers and one that I like. For lead fowling, shooters choice is my go too.
Back to copper cleaning prior to my digression, words of warning, do not mix these copper solvents with any other cleaner. Do not leave your gun un attended, clean the barrel out after a few minutes as per the directions and re apply. The blue color on your patch is the copper. When you run out of the blue stuff, run some dry patches through or some with brake cleaner. Then apply your gun oil. I like mil spec gun oil, but to each their own on oils.
Why not mix the copper cleaner with our cleaners applied with your patch, you might ask. It sets of a chemical reaction that pits the barrel.
Why not leave the copper cleaner in your barrel? It is too aggressive and will etch your barrel.
Your barrel is rough and that’s probably why it’s copper fowling, unless your just shooting a lot. Might think about lapping your barrel.