Once you've finished the game the first time, you'll unlock Assignment Ada and the mercenary missions. If you can complete all of the mercenary missions with a 5 star rating, the handcannon will be available to purchase when you start a new game on your cleared game.

getting the hand cannon will take a whole lot a work and a whole lot of time. you have to get a 5-star rating for each one of the characters on all 4 stages of mercenaries. to me that's the hardest challenge in the game because i haven't even come close to doing that yet.

yes, you r right, but u left out one thing. At first i thought i was to gte a five star rank with each character, but thats not all, you have to do it with every character and in every damn map. The hand cannon is the hardest gun to get. But if u want my opinion, the all mighty world war II classic thompson machine gun wins my vote. Its really like a gift from god. ENJOY =)

Well you have to beat the Mercenaries mini game and get five stars with all the charecters in all the stages,then the merchant will sell it to you free but you can upgrade it.
See ya