USP Bore Paste Gun Cleaner and Barrel Break-In Kit USP Bore Paste is an abrasive paste that is softer than steel but harder than barrel fouling. It is great for removing carbon, lead, and copper fouling from your gun barrel. When heavy bore fouling is present, you can feel it being removed as each rod stroke with USP Bore Paste feels smoother and smoother. We've gravitated to USP Bore Paste as our first choice for a cleaning process during break-in or seasoning of any barrel. Being a softer-than-steel abrasive substance, Bore Paste works kind of like sand paper to remove any kind of fouling quickly and reliably... Without harming your barrel (Remember it is SOFTER THAN STEEL). Bore Paste removes carbon, lead, and copper equally well... Which makes it an excellent first choice cleaner for use in break-in or seasoning of all gun barrels. (You can feel the barrel getting cleaner with each stroke). This cleaning kit includes bore paste and gun oil. Clean your barrel with the bore paste. Then swab it with the gun oil afterwards. You will need a sub caliber bronze bore brush, jag, and patches to apply the bore paste and oil.