One of the four, Tran Quoc Cuong, scored 555 points and bagged an individual silver medal.
In the same event for shooters at the junior level, To Van Tuyen earned 527 points to finish third.
In the women’s 25m sport pistol, Le Thi Hoang Ngoc only managed to carry off a bronze medal with 573 points.
Vietnam’s hopes for other medals are pinned on the trio Ha Minh Thanh, Bui Quang Nam and Kieu Thanh Tu, who were scheduled to compete in the men’s rapid fire pistol event later the same day.
The SEASA tournament will end on June 9.
After the championships, Ngoc and her teammate Hoang Xuan Vinh, who have already won berths for the London 2012 Olympics, will attend a training session taught by expert marksman Park Chung Gun from the Republic of Korea to prepare for the Summer Games in July.