Mosin Nagants are the absolute toughest bolt action rifles in the world.
I second that. If someone can break a M-N, they either have too much aggresion or too much time on their hands.
1917 and P14 enfields are way overbuilt and are tough.
1903 and 03A3 Springfields I've never considered rugged. They both have relatively delicate sights and firing pins.