Just run about 3 or 4 Brake cleaner soaked patches through the bore, dry patch, then oil patch. I've been using nothing but patches soaked in brake cleaner to clean my Finnish M39's bore since I got it, with no ill effects and the bore is just as pristine as when it was new. When copper fouling becomes a problem, I clean first with the Brake Cleaner patches, then apply Sweets 7.62 for the jacket fouling, then Brake Cleaner patches to remove the Sweets residue, oil patch and done. We are not at war, and not on maneuvers in the field where the only thing available to clean might be water. Brake cleaner works just fine for me, and I'll continue to use it for cleaning the bore and all metal parts. Keep it away from shellac finishes though.