Now this is from memory.. and I'm older than dirt and the memory is the second thing to go so take this for what it is worth.
It seems to me that I recall reading in Hatcher's Notebook that a Springfield 03 fired a .45 ACP down the .30-06 tube without a problem!
Now the biggest reason I doubt that is I don't think there is enough energy in a factory .45 to swage the bulet down to .308! I guess I better do some research right now before you guys blast me!