I've used them all and use HBN now. I think WS2 is most effective negating copper. HBN is so much easier to use I stick with that. HBN really seems to help alleviate carbon fouling accumulation. In my 204's I still use naked bullets.
I'd suggest you buy some Patch-Out and the Accelerator that goes with it. I'd be willing to bet Sweets is missing some copper in the throat.
I've seen quite a few factory and milsurp barrels Sweets could not fully clean that Patch Out will.
Having ammonia etched copper deposits left in the throat seriously exacerbates your problems. Gotta get it all out before you can think of eliminating it.
Once its fully clean I'd then suggest you buy 1lb of Winchester 748. Load some up and start shootin.
You may or may not find an accurate load with 748. Does'nt much matter. Pay attention to the copper fouling in the muzzle.
Should be drastically reduced just by switching to a sootier ball powder. H-4895 is just running too clean for your barrel. Not uncommon at all for prolonged shooting.
I've shot over 400 naked rds using 748 in my barrels. Barrels that would copper up and go south quick using Benchmark.
I would'nt think of bringing a 204 to an egg shoot unless I have at least 100rds of fouling in it. I usually only clean them out of guilt.
Once you begin to understand the correlation between carbon and copper fouling you can decide on trying different powders if 748 isn't giving accuracy. H-355, Tac, X-Terminator are a few that come to mind.
Of course some powders give too much carbon. Any powder that steadily accumulates carbon will give inconsistent accuracy just like a powder that allows steady copper accumlation. You need to find your barrels balancing point.
I agree with Silverfox. Hornady seems to copper the most. Berger the least. You might want to try some 39bk's. Drop the velocity a bit by using a heavier bullet. Velocity reduction always helps.
Try some 748. If that does'nt cure it theres still other methods
Always have a very light coat of oil in a clean bore for your first fouler. Don't start with a dry bore, thats just asking for trouble.
Bronze brush! 