I remember Sly Stallone was going to carry the Browning for the end of Rambo. He could carry it, but firing was another matter. Gonna need a hell of a lot of strength to carry the gun + ammo and ammo pack and to handle the recoil.
you know, it would not surprise me at all if the M-2 still saw limited use by the time your story takes place. the Springfield 1911 .45 magnum will be a highly values collectors, probably spawning modern (in the time of your story) firearms that share appearances simply because of how iconic the weapon is.