I have been using the IMR 4166 in two rifles here recently and cleaned both guns this week-end. Both had about 50-60 rounds since being cleaned. It seemed to me that the powder fouling seemed excessive and took more passes to get it all versus say IMR 4064.
I have also noticed that when I use CFE223(another Copper removing powder)that the residue is also heavy and very black BUT quite easy to get out quickly.
These two rifles took soaking with bore foam a couple of times and numerous patches with KG1 to get them clean. Not much copper but I don't think these get much copper.
I will also add I use Reloder 26 another supposed copper removing powder in several guns and it cleans up quick and easy.
Just thought I would post and see if anyone else noticed similar.
I know I won't hear from FiremanFG as he only cleans every February 29th ...