Found old bullets in Nor-Cal AGE? Cherry Picked?

[JV]

A friend and I stumbled upon a hill in Northern California with literally hundreds of the larger pictured bullets and some of the smaller ones.
Funny thing is there was NOTHING else besides these bullets. Probably another detectorist came through and cherry picked it already?
The next day three of us went back and hammered it and the neighboring fields HARD for 5 hours and all of us had nothing but bullets at the end???
Could it really have been that well cherry picked? Any idea of the age of these bullets?

 

[burlbark]

The one on the far left has the look of being pretty old, those huge lube grooves. The one on the right doesnt look that old to me with the machined groove rolled in place. I am here in Northern Ca, what neck of the woods are you?

 

[Larry (IL)]

The left bullet looks to be a post civil war 45-70 and the one on the right is more modern yet.

 

[Flintstone]

I would say you are at a target range. If you can look 2 to 5 hundred yards you will find a old store or blacksmith shop that worked on guns. Flintstone