The serial number and the caliber designation are engraved on this one rather than stamped, not that it is of any importance either way. I've never gotten half inch groups out of the .411 on a regular basis but have had a number of cloverleafs with the discontinued Barnes 325 gr X. Most are between and inch and inch and a half, which is plenty good for a thumper! The still available 300 gr X's are usually between 1.5"-2".