For the most part, functionally they are the same but visually they are different and it all has to do with the contour of the stock. The 77, has a flat bottom and the 10/22 is rounded. If you install a 10/22 in the 77 well the base stick further up into the well. The countours are just not the same. They may function well but look like crap. Still waiting for
geoman458 to confirm what magazine is in the well ...
Be Safe !!!