Was fifty guns a large artillery concentration?

Were fifty guns really a large number for an army of Grant's size?

Yes; for a manoeuvring army at this point in the Civil War, fifty guns concentrated on one defensive line represented major firepower.

Fifty guns were a substantial concentration for a manoeuvring army at this stage of the Civil War. The Confederates also assembled a large battery elsewhere in the battle. Both concentrations were substantial in the context of Shiloh.