Agreed the hand guard appears to be for the Model 1901 rear sight. The sight you bought appears to be a Model 1896 both correct for a model 1898 Kragicon but shaped differently. Krag screw holes are placed the same so any model rear sight, 1892,1896, 1898(discontinued because it was calibrated for "too hot" new ammo), 1901 and 1902 will fit, but hand guards are design specific.

http://kragcollectorsassociation.org.../867202750.jpg
http://kragcollectorsassociation.org...iflesights.jpg