Vietnam veteran Marines and some of their family members fire a simulated verson of M9 9mm pistols at the School of Infantry's Indoor Simulated Marksmanship Trainer, Camp Pendleton, Sept. 10. The group spent several hours touring SOI's facilities and remminicing about the Vietnam era. - Vietnam veteran Marines and some of their family members fire a simulated verson of M9 9mm pistols at the School of Infantry's Indoor Simulated Marksmanship Trainer, Camp Pendleton, Sept. 10. The group spent several hours touring SOI's facilities and remminicing about the Vietnam era.