Okay, you're free to disagree, but I stand by my appraisal that it is a late-1880s (at the earliest) to 20th-Century bullet. Hopefully, we'll see what other "projectiles guys" like BosnMate, Nhbenz, and perhaps Pistol Pete have to say about your bullet.
Meanwhile... I am 100% certain it is not either of the two varieties of civil war .36 Savage bullet. Your bullet's base below the groove is too short to be one of those. Also, its nose-shape doesn't match them. Also, they are listed as being .380 and .388 in diameter (when unfired). Afterward, they are somewhere between .365 or a bit more, depending on the height of the rifling-marks.