yeah it is hollow pretty heavy is why im assuming it to be iron,it was about 6 yards south of the bullet,James thats what i was thinking it look like a cylinder pin and being hollow in the front makes me think it would have to be a gun just wish I would have spent a little more time investigating the area but im limited to hunting late evening and dark do to work right now.I hope to get some time off in the day to get back to the spot.Thanks for the replys guys I am pretty new to all this just bought the detector a couple days ago but im hooked.