OK, I hate to do it, and I apologize for the debate that may follow. I'm not finding much council in my search on what is reasonable to shoot through an Elsie in sound condition, and the arguments on the other collector forums are not from the perspective of L.C. Smith (maybe that doesn't matter).
What I'd like to shoot is Winchester Target 7 1/2, 1200fps, 1 1/8oz, or the same in the form of Remington Gun Club. Federal, Estate, Rio have their versions of the same as well. They're cheap, readily available, and seem an appropriate load for an old, stout gun in sound condition.