I'm aware of the R-P connection, and that Peters was once an independant company. And longer ago than when my found cartridge was made I imagine, since the 250-3000 may have come out (c. 1919?)after Remington had already bought them up. It was just fun to speculate about the circumstances of this one round so that's why I asked about the "Peters" headstamp.
A few miles away I also found a fired .30-06 case with "SL" and "43" just laying on top of the leaves, much tarnished but otherwise in good shape (I know, St. Louis/1943). I like to imagine it was fired by some guy with an old Springfield, maybe a logger after the crew knocked off for the day since it was near a grown-over logging road. Of course that and the 250-3000 could have sat in somebody's drawer for 50 yrs before being used, but it's more fun to imagine ghost hunters walking the woods.
I'm also old enough to remember those Peters shotgun shells, may even have a few still laying around that I didn't shoot from my old Mossy bolt action 12 ga. Thanks for all your input, this is a great site.