Primers.
They all make small pistol primer brass for 45acp. Lead free is the reason. Originally only made in small rifle and pistol whether or not large is next, don’t know. But the EU mandated non toxic primers in 2015.
Small primers question:
What I have learned:
(By headstamp)
Blazer (Brass)
CCI
Federal
S&B
Speer
Win (NT)
Winchester