Found these on the beach. The larger shell measures 2.38 inches in length and 1/2 inch in diamter. The smaller, heavier one measures 2.26 inches in length and 0.41 inches in diameter. Thanks!
20th Century copper-jacketed lead .50-caliber rifle or machinegun bullet, and the same ID for the other one except it is .40-caliber or a "nearby millimeter" equivalent.