Hummm, I'm not familiar with that word as firearms terminology, but I am familiar with the word "obdurate".
Obdurate is synonymous with unyielding, inflexible, callous, or stubborn. That just didn't seem right to me.
A little googling and I found that the term you meant is actually "obturate", which means to block or obstruct.
As to the bullet. I really don't think you will have too much luck dating it.
It is in the family of a Minie ball, and as such, would have seen use dating back to the civil war, but such bullets are still in production. You can still purchase molds in those sort of shapes, and black powder rifles to go with such bullets. The corrosion visible is typical, and forms pretty rapidly.
I can say that it was neither a standard issue Union nor Confederate Civil War bullet. Those were pointier, and had different groove designs.
Anyway, even if it were a Civil War fired bullet, the value isn't that great. Maybe a couple of bucks. So many millions were fired, and so many are still waiting to be picked up in so many battlefields.
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