I was trying to come up with the proper name for the lines in the chamber of an HK barrel. They run along the length of the case. From the shoulder to the base of the case. They help the extraction with the roller block action of an HK.
In the MP-5 they are about ¾’s the length of the case.
They leave 6 or more black lines along the length of the case after firing. These are just gas marks not actual dents or changes in the brass.
but nothing cleans brass like stainless steel pins with liquid cleaner in a rotary tumbler
I dont have a tumbler but that sounds like a good idea.
"The difference between stupidity and genius is that genius has its limits" Albert Einstine