So you think your barrel is clean? Well here’s a way to check how good your cleaning method really is.
Clean your barrel as you normally would but before putting it back in your safe run a patch soaked in Hoppe’s No.9 through it. Leave it to soak overnight or at least 12 hours and then run a clean dry patch through and see what colour it comes out.
Usually it’ll be either a green or blue colour which indicates that there’s still some copper fouling present and the barrel could use some extra cleaning.
The picture below is of a patch that came from a supposably clean barrel. The barrel had been given a Sweets 7.62 treatment the night before but it had failed to remove all the copper.
I leave Hoppe’s in my barrels permanently and it’ll usually take several overnight applications before no more colouration occurs. Probably not really necessary but it’s nice knowing the barrels are as clean as possible.