GMM brass from the late 80s if that makes a matter...
Yes, it does matter..................FC brass in general, was much harder & would handle more pressure than anything else during that time frame.
If I bought brass to run hard in any of my BG guns during that era, it was always FC if I could get it. And I know Bob Hagel even wrote about as being the hardest, & thickest in the case head area with the least primer pocket expansion.
Can't address the 223 stuff at that time, though, so I don't know if it followed that same line.
