the reason the reb gunners were over shooting their targets was because of the fuses supplied by the Confederate ordnance dept. Until the late spring of 1863 all fuses for ANV artillery came from the Richmond Arsenal. The fuse manufacturing facility blew up in May. CSA ordnance ordered another arsenal further south (Selma, I think)to supply the ANV fuse needs for the invasion. the other arsenals fuses when cut to the same length as the Richmond fuses actually exploded a couple of hundred yards further in range. The CSA ordnance dept. did not discover this disparity in fuse performance until after Gettysburg.
Thank you. I was not aware of that problem.