Around about 1835,rifle makers in this country tried to improve the accuracy and range of their rifles by making a longer,more streamlined bullet than the round ball.These rural gunsmiths first tried what were called picket bullets or sugarloaf bullets.For better accuracy,they were started into the muzzle of the barrel with a straight-line seater.They did improve range and accuracy to twice the range of round balls.But after a few years the bullets were made with part of the length having straight sides more like modern bullets.These were called cylindro-conoidal bullets,and were a vast improvement over the picket and sugarloaf types.The bullet in the photo looks like a sugarloaf style of bullet to me.If you want to learn more about this evolution of rifle and bullet development,refer to "The Muzzleloading Caplock Rifle",by Ned Roberts.It's an old book,but might be available from Dixie Gun Works.