Was planing down some Aspen today and found a bullet It's just shy of 5/16 diameter. I don't have any calipers to get an exact measurement. Sure glad it was lead and not steel. I've found barbed wire and rusted nails and screws before but this is a first for me.

Looks like .30 carbine to me. What does it weigh?

I don't have anything to weigh it with

I came across a bunch of shot in some ash 8/4 boards when I was building my workbench top.  I didn't see them before I jointed and planed the boards (rough cut kiln dried), but I did see some unusual grain and coloring in the area before it showed up.  I would guess it was no6 shot - hit several pellets.  The face of the board where the pellets are, got glued up and is somewhere in my bench top.  The spot is closer to the underside of the bench, so they wouldn't show when I planed the top flat.
I don't think I have even found n a bullet in any of the trees I have cut down or sawed up for firewood or lumber.  A few nails and even a couple rocks.

I planed up some local oak for a bed I was building a few years back that had 3 lead rounds in it.  I left them in place and finished over them just because it was cool.

I picked up a digital caliper and it measures .385.

Nice idea.

I've found a few bullets over the years, not many as intact as the OP's though.

Google says it's a post-1890 .41 Long Colt.

Oddball.  Jacketed?

 

Lead core and jacketed

None were jacketed.  Most likely it is a deformed .38 special bullet.