In campaign on Infernal Mode, Keith can find this weapon during Episode 9-1. It has capacity of 28 rounds and maximum 80 spare rounds. Also, this weapon can be obtained after scanning all 30 hidden handprints, so it can be used in Episode 12-2 against Ultimate Abyss and after that it can be used in further completion of game if playing "New Game+".
In Raid Mode, the stats are generally the same as in the Campaign but varies depending on the player's level. It is found rarely in the store, usually with a very fast rate of fire and a high capacity.
"Has less firepower than the standard issue PC356 but makes up for it in load capacity"
Jessica's FBC issued G18 appears only in the HD port of Revelations as one of the 3 Weapons DLC. It has a two tone color instead of being completely black. Gameplay-wise, the weapon's stat focuses more on the Firing Speed and Capacity to compensate for its weak Firepower. Strangely, the weapon's description compares this weapon with the PC356 rather than its original counterpart.