Howdy... and welcome to the forum!

First of all, if it IS a carbine, then someone added the sling and swivels.  Without seeing the S/N and better pictures, my guess is that it's a cutdown rifle stock.  Also, the receiver Peep sight is not original.  As Culpeper said, better pictures will tell a lot!  Post pictures showing the follow:  Left side of the receiver showing the markings and especially the S/N, good clear picture of the front sight post as it's mounted to the barrel.  a picture of the muzzle crown, and an overall picture showing the right side of the stock.  Like Culpeper said, run a cleaning rod down against the closed bolt, mark and measure.  22 inches exactly may be a carbine barrel, but does not guarantee it (the sight post could have been reattached to a cutoff barrel).  Anything other than 22 inches is definitely a cutdown.