This is an unusual M91 Cavalry Carbine in that it is a cut down rifle with cavalry rear site and a rifle stock that has the forend patched where the spring that holds the band was. Sling swivels are on the bottom of the stock instead of on the side

Stock is not flush with the front sight as it should be for a Calvary Carbine Who converted this gun I do not know but there were some converted from rifles in the 1960's