I never heard of Paul McCartney being termed as just "Macca" until I first came to this Message Board.

Have I been in a cave somewhere, or is "Macca" universally accepted?

He's been called Macca since the early days. You hear John refer to him as Macca on one of the Anthology CD's when he breaks the glass, Bono even called him Macca at Live 8. I've seen it in magazine articles, in books, and on other boards as well. So yeah, I'd say it's universally accepted.  

Quoted from Buttmunker

I never heard of Paul McCartney being termed as just "Macca" until I first came to this Message Board.

Have I been in a cave somewhere, or is "Macca" universally accepted?

I think you've been in a cave!

He's been called it a long time maybe as far back as caveman days

Quoted from Sandra

You hear John refer to him as Macca on one of the Anthology CD's when he breaks the glass

I heard John call him Paul when Paul broke the glass during the take on "You've got to Hide Your Love Away" (Paul's broken a glass, broken a glass...)

As far as the rest, I'll try and shave the caveman hair off my shoulders.

ah yeah but just after that he says "oh, you ready....Macca" at 24/25 seconds into the take!

I don't like to call him Macca. I feel it a little stupid. I generally call him Sir Paul!  

Yeah, it's universal.

I'm sure it's pronounced Mack-uh, but other people on other boards thought it was pronounced a different way. I'm right, aren't I?

I've always pronounced it Mack-uh as well.