Matilda is a handgun that can shoot 3-round bursts when equipped with the Matilda stock. Since it is the only handgun that can shoot anything other than single shots, it has high firepower but consumes a lot of ammunition.
A lot of spinel is needed to replace Matilda. Matilda's main body requires 10 spinels, and the stock that enables a 3-round bursts requires 12 spinels, for a total of 22 spinels. If you want to exchange, complete the blue request notes to acquire spinels.