The stock appears to be a cut down rifle stock and the front sight is definitely not original. The stock forend past the forward barrel band is to long and in the first picture I can make out that it has a retaining pin for the barrel band. A carbine stock would have a retaining flat spring for the barrel band and not protrude as far past the barrel band. The sight appears to be a Springfield M1903 which is a common replacement when a barrel has been cut down. Others can evaluate my observations further but IMO it looks like a cut down rifle. If it is safe to shoot, then enjoy the smooth action and have some fun.