I don't think the action is shorter on a model 7, or they would not accept the chamberings that they offer. They chamber them in .308, .7mm-08, .243, and .260, which are shorter cartridges, but still chambered std on the 700 short action, which is the same action used in the model 7.
The main difference in the 700 and the 7 is that the 7 was introduced as a light fast handling carbine type, that would compete in size and weight with lever guns, yet provide the same strong action and great calibers of the 700 short action.