Jason:  Top Dean is partially correct.  Your 1899 Carbine does not have the Carbine Hand-guard for the 1896 sight.  You appear to have a Rifle Hand-guard for the 1896 sight.  I think the original sight for a Carbine in the #282xxx range was the 1898 Carbine sight with the 1898 Hand-guard (which was identical for rifles and carbines).  You can view photos of the various Krag sights and hand-guards by  'clicking' on KCA Website at the top of the forum page.  This will take you to a Main Page and you then select the Tab 'Photos'.