As my posting-name suggests, artillery projectiles are my specialty-area of relic study. Not enough information and photos were provided to enable us to do more than "theorize" about this object. For example, you don't say what country it was dug in. You gave us a view of one end of the object, but not its other end. Also, the photos are distant-view, instead of closeup views needed for accurate identification.
I'd at least like to have seen it with the thick dirt-encrustation washed off.
Its shape more resembles a "necked" artillery casing than a projectile. Also, it is EXTREMELY long in comparison to its diameter... which suggests it is a casing rather than a projectile. However, that object appears to be rusty, indicating it is made of iron/steel. Artillery projectile casings tend to not be made of iron/steel. Therefore, this object might not be an artillery object.