Most people still call it the .45 ACP, me for instance. It was .45 ACP when it was invented and it is still the .45 ACP in my mind and in many others as well.
To correct someone on a point this trivial is beyond ridiculous.
.45 A(utomatic) C(olt) P(istol) or .45 auto, same difference.
I only correct the new shooters and people giving advice to new shooters. Calibers are confusing enough without giving designations that can’t be found on newly manufactured boxes. Trying to teach new shooters, I try to keep it as simple as possible. I don’t go through the history of their guns. I also try to keep the designations as simple as possible. It’s tough to remember three hundred years of history when all a new shooter wants to do is hit a paper target at fifty feet.
As a teacher it’s a constant reminder that I can’t teach what I know. I have to teach what is needed. Help the guy find that box of ammunition as it’s printed on the box.