The basic ammunition load for each infantry soldier was 40 rounds in the cartridge box. When a large action was expected 20 additional rounds might be issued to each soldier, who placed them in his uniform pockets or knapsack. In addition, 100 rounds per man were held in the brigade or division trains and 100 rounds in the corps trains.
Ballard, Ted; Arthur, Billy (2014-07-16). Chancellorsville Staff Ride: Briefing Book [Illustrated Edition] (Kindle Locations 1129-1131). Pickle Partners Publishing. Kindle Edition.