After finishing a quest, by escorting two American tourists to an airport, John C. will send you an email, and mentions some big guns which he has modified for a bigger punch. A few days later, arrives at the airport containing two of these guns. They fire 7.62x51N ammunition. The AMT Automag III is featured in the game, and has been re-chambered to fire 7.62x51mm rounds from a 5-round magazine. This is the description for this handgun in Back in Action.