I've got a few PK brakes and they work unbelievably well. Been shooting quite often with the braked rifles and like to keep the brakes clean. While cleaning the rifle bore with Wipe-Out I decided to give it a try on the brake too. I laid the brake on a clean rag and sprayed the foam into it. Almost immediately light blue foam started to expand out of the ports. I was surprised because I always assumed that only carbon deposits collected in the brake which is why I usually use a carbon remover in them. The blue foam would indicate that copper was present in some form or another. Any thoughts on this?