Unless this is like some local election practices, the same man can't have died in March 1863 and enlisted in September of the same year. Charles M Byrd of Capt McNair's Company, 3rd Mississippi Battalion, enlisted at age 18. He appears on the 1860 census for Pike County MS at age 17. Charles B Byrd appears on the 1860 census of Perry County MS, age 23. Evidently this son of Hezekiah Byrd survived the war as he is reported on later census records.