Ambassador

First , www.teamfortress2.com/spyupdate/ (day 6)

Someone on the steam forums was very bored and decided to calculate how big the gun actually is…

http://img.photobucket.com/albums/v401/aboojumsnark/ambassadorcaliber.jpg

.885 cal apparently.

For comparison sake :

AWP from CS = .338 cal
Anti-Vehicle Rifle = .50 Cal

Cant wait to wreck people with this thing.