I didn't know if it had been shortened or if it was a different hand guard, but you are correct. It should go back further and cover the receiver ring.

The Kragicon Collectors Assoc site has two photos that show a correct rear site and hand guard. The sight is next to the barrel band and the hand guard is shaped differently to fit the sight's more forward position.
(This is also how it's shown in Canfield's book)

Photos

As said before there should be a 'C' stamped on the sight as well and the front sight should be cut into the top of the barrel.

In the lower part of the first page of this older thread, Badger shows a photo of a carbine rear sight and the inlet front sight -

My 1898 Krag - Is It A True Carbine?