You can't use Spire point bullets like this in a 30-30 or any other tubular fed rifle without serious risk
of more excitement than you asked for. The single shot and bolt rifles in that cartridge could but that ammo would have to be reloads since the Factories won't load it. This particular projectile from the pictures appears to have a concave base. No new pictures since he cleaned it....and no actual diameter measurement. Other than it was found in the North-East.... I doubt much more can be determined. I would guess it to be at least post 1900 since popularity with jacketed ammo in the U.S. prior to that was limited to the long and round nose projectiles like the Krag and Carcano cartridges used. So...a hundred years is a pretty big window. The patina on the copper looks pretty thick.
With no other information and guessing it is .30cal and weighs approximately 150 grains I'll venture out further on the limb than the others here and say "Its a U.S. .30 Ball Projectile of 1906."
The 30-06 was adopted in 1906 as the "Ball Cartridge, caliber .30, Model of 1906". The nomenclature was eventually shortened to the well known "30.06".
The round designated as "7.62 NATO" wasn't adopted until the early 1950's and was a replacement for the U.S. M2 .30 round mentioned above.
TiredIron