I can’t believe this rifle would have seen action in Vietnam unless it was a personal civilian weapon stored in an embassy. The embassy in Saigon was overrun at on point. A varmint caliber rifle in 22-250 would be a liability in the field. You would be limited in the ability to replenish ammunition. At the time the standard military ammunition was 7.62x51, 30 cal (30-06) and 223 Rem (5.56x45).