They shoot a 110 RN bullet at about 1900 FPS. Not the best big game hunting round out there but would be good for small game. They are a heck of a lot of fun to shoot.
Better yet shoot them in the CMP GSM Carbine Matches.
But you really hit it on the History Aspect. Yes you should check out your grandfathers Carbine and ask him about it.
My Underwood CMP Carbine was made in 1944. I got a used carbine sling from CMP for mine. The sling has a guys name carved in it. My wife did a search on some military sight and found there were two soldiers that same year, with that name who fought in WWII. One in Europe and one in the South Pacific.