What would be the diameter of the neck if it were complete? They came/come in all sizes, and many were small since the nature of use was generally medicines. Here is a website with some modern wooden ones where the Mortar is only 2 5/8" in diameter x 2" to 2 1/4" deep. http://www.crafty-owl.com/mortar-and-pestle.htm
not a piece of pipe..it has no threads. looks like if you followed the contours it formed a complete container. With out having it here with I am going to guess you could put your thumb in the top with no problem but certainly not much else.
I am not claiming it's a relic but a civil war battle did occurred in this area. I originally though it may have been a grenade but the shape did not match anything of that era so I am sorta stumpped as to what its from. I also searched a civil war re-ennactors supply web site and again nothing ever came close to this. Again - I am stumpped.
Maybe the bottom piece of a stool or leg that fit over the wood. Kinda similiar to the ant trap ones on my hoosier. May have had a caster in the other end?