Nashville Arsenal's Captain M.H. Wright left surprisingly good documentation of the type of haversack he was contracting for in late 1861 and early 1862, and appears to have continued requiring the same design when he shifted operations to Atlanta later that year.  The bags were made of cotton canvas or osnaburg with an inner divider and single button closure.  While no haversack with a solid Nashville or Atlanta provenance is known to have survived, there are several identical original haversacks that match the general description.  These reproductions are made from custom woven narrow width osnaburg with a period selvedge, as is necessary to reproduce this haversack properly.  And as a bonus, these bags are huge!

Nashville Arsenal Haversack - Shiloh