Howdy,
I think the Trapper only holds 9 rounds. IF you want to reload an extra caliber or just shoot Schofields in everything, you can get 10 of those in. As for feeding reliably..... some will, some won't.
There are plenty of Pards that shoot the trapper. Once you get the hang of it a one round reload, if the stage calls for 10, is pretty quick. So, don't give up on the idea completely.