Note that a repeater (pump, semi, or what have you) may run into unexpected problems with short shells. Some 3 1/2" Uber-Duckhammer pump guns have lifters that don't feed 2 3/4" shells right, tending to flip them around and try to load them backwards or sideways or suchlike.
Other than that annoyance it's safe to shoot any shorter shell in a long chambered shotgun. Also note that unless you try really hard you can't chamber a 3" shell all the way in most 2 3/4" only chambers.