I have a M1 training film that shows cartridges with wooden bullets in use. Apparently the Army determined that the soldier needed lots of practice with the funny "en-bloc" loader, and running the op-rod back to chamber a round.
Later in the film a "coach" is shown laying beside the prone soldier to help with dry-firing, to master trigger control. The coach would wrap his hand in a handkerchief, or wear a glove, so that he could smack the op-rod, both cocking the action and simulating recoil. Didn't see the wooden bullets in use for this part, so I'm guessing it was restricted to loading practice.