Al about the .45

[model 70]

so i am looking at getting a semi-auto pistol. what's up with the .45?

now i know the cowboys shoot the .45colt. what cartridge is fired from the 1911's? like the ones from WW2.

my buddy has a springfield .45 that i've shot. i like that gun alot. is that the .45acp?

i like the idea of hurling a big, heavy chunk of lead at someone who is trying to do me harm. so why isn't the .45 as popular as the .40cal for home protection?

any downsides/upsides would be appreciated. thanks.