[mountainlion]

You don’t know how many rounds you need until it’s over, and that’s assuming you have some left.

Things could be over with your last round. Backup gun(s) would be a good idea. A gun could fail.

[null and void]

You don’t know how many rounds you need

I know I'll never need more than seven.

My betters told me so.

[MV=PY]

"Things could be over with your last round. "

True. But I always try to plan for leftovers. ;-)