Last week I video taped pretty much what you describe but with a decoy. There was two gobblers beating on a decoy but for 12 minutes one of them kept pecking, mounting, beating the decoy even though it lay on it' s side. The other would leave, come back, leave, come back. It was almost comical. It does show how ruthless gobblers can be on bird lower in the pecking order.

btw.. the decoy' s head is all pecked up. They go for the eye!