If it is a post WW2 bomb tail, have a look around the front (open) end of the unit. If my memory serves me right, there may well be at least 4 threaded holes that would have had allen key headed bolts (for want of a better word). These were screwed in to locate the tail unit over a flange on the rear of the bomb body that contained the explosive, or concrete, depending on if it was a live bomb, or a dummy.

Regards, Cabbage