Maniac Detector, your bullet does resemble a civil war era Maynard Carbine bullet. However... you said its length is 3/4-inch and its diameter is "over 1/4 of an inch bore." In the photo, it looks less than 1/2-inch diameter, so that excludes one of the two calibers of civil war era Maynard bullets. The other caliber was .36-caliber. The shape of your bullets nose is different from the civil war .36 Maynard bullet. Yours MIGHT have been "whittled-on" -- which would explain the sifferent nose-shape. We need super-precise measurement (in hundredths-of-an-inch) of your bullet's diameter, measured slightly above the groove. If it isn't "right-at" .36-to-.37, it isn't a civil war era Maynard bullet.