I was hunting a Confederate defensive position and digging a lot of bullets, shell fragments, etc.  I got a deep but good and repeatable signal.  But it was in very hard clay.  I dug a hole the length of my arm and it was very, very tough going even with the Lesche relic shovel.  I got to where I couldn't reach the bottom to retrieve the dirt and enlarging the hole in that hard soil was beyond my endurance.  With much regret, I filled the hole.  I am fairly certain I am dealing with piece of artillery.  I am going back.  This time I will bring a pick axe and go straight to that spot first thing.  I am determined to find out what's in that hole.