jwall, the first two that came to my mind were the two you mentioned, 30 WCF and 30-06. Then Dollar threw in the 45 Colt and 45-70. I guess for me it would have to be the two latter as I've shot infinitely more of them than the two 30's. However, I'd bet there's a lot more users of the first two than the latter two.
NOT to argue there sharps. I guess living the South and not knowing anyone personally who has travelled to hunt Moose or
Buffalo or Big Bears-----> the 45-70 never came to mind. I know 'some' of its history and it CERTAINLY is American !
Jerry
