Bright Blue generally means copper fouling.
Dark Grey or black is generally powder fouling.
There is another color for lead fouling, but since I never shoot anything that involves lead fouling I can't help you there.
This of course assumes you are using a cleaner that doubles as a copper solvent / cleaner (like Sweets 7.62 or shooters choice). If not, then you'll only see the grey/black from podwer fouling.
JeffVN
Dark Grey or black is generally powder fouling.
There is another color for lead fouling, but since I never shoot anything that involves lead fouling I can't help you there.
This of course assumes you are using a cleaner that doubles as a copper solvent / cleaner (like Sweets 7.62 or shooters choice). If not, then you'll only see the grey/black from podwer fouling.
JeffVN