1903A4 production was not continuous, in one case they made around 2,900 and quit for a while. A request would come in for more and they would make another run. If you post your serial number, anyone here can tell you what barrel is (originally) correct for it, also, some of the members can run an SRS check and see if there was anything specific to the rifle. Correct barrels are not always the same month that the action was stamped.