It was used for artillery practice in the mid 1920s when it was called "Gigling Reservation," the predecessor of Fort Ord.
See 76TH FIELD ARTILLERY REGIMENT, 2ND BATTALION at the Presidio of Monterey.
Other artillery practice in WW II and after included 81 mm mortars, 105 mm howitzer projectiles, and self-propelled 8 inch artillery explosives.
Munitions removal will be complete by 2022. It’s a long process that begins with clearing vegetation then a survey team searches for unexploded ordinances. Through 2014, more than 50,000 shells had been collected. See Fort Ord 20 Years Later by Krista Almanzan, Sept 26, 2014.