Got me. I don't know either. I bought some from a member who posts here and bought a bunch from Ammoman.com.
When I log onto their website now, the .308 page is almost empty and the .223 just lists blanks.
Ammoman just listed Hornady 110 gr. TAP for. . .are you ready for this. . .$199 for 100 rounds delivered.
Not sure how effective blanks would be
Either one is hard to come by today as is 22LR.