As a small arms instructor and range safety officer, I frequently see AR platform rifles lock up using steel cased ammo. Many think it is due to lacquer on the case to prevent rusting gumming up a hot chamber. But is that really the reason? And will steel cased ammo really damage your AR?
There are a large variety of small arms cleaning kits on the market. Some good, some not so good, some inexpensive, and some over priced.