All I could find was GBW Cartridge Company. Midway, Midsouth and others selling both loaded ammunition and new unprimed brass . Might be another source !
Gary
I've never used it in 223. I've used gbw brass in 45 acp. Decent. Nothing to write home about but gets the job done with no problems. According to several posts on a couple of other forums the brass is made by Remington. I take that with a grain of salt however. Search on google didnt turn anything definite up.