I am attempting to do a drawing of one of my ancestors who was a Private in the US 23rd Missouri Vol. Inf. at the batlle of Shiloh in 1862. The only photos that I have found show three members in Frock coats and kepis(not forage caps) and was taken in late 1862 after the unit had been exchanged as prisoners. I wanted to know if the unit would have went into that battle in frock coats or in sack coats. Also would kepis have been issued rather than forage caps.I am thinking that the uniforms in the photograph may have been a photo studios on-hand stock for soldier customers. Any help would be greatly appreciated.