He is incorrectly listed at Findagrave.com as Robert Packer, but his unit appears to be correct.
http://www.findagrave.com/cgi-bin/fg.cgi?page=gr&GSln=packer&GScid=98817&GRid=17342142&

Robert's younger brother, James Hiram (Jr.), was also a member of this same unit. They were residents of Leake County in 1860 and in neighboring Neshoba County in the 1840 & 1850 census.

Military and pension records are available at this site.
http://history-sites.com/research/index.html