As seen in episodes 9 & 10 of season 1. Retouched screencaps below the jump:
The pistols appear to be identical to the rifles, only with the stocks removed. Someone online noticed the similarities in shape and proportion between the Protogen pistols / rifles and the Magpul FPG. I think he’s correct. KWA made an airsoft version of the FPG, and there is a horribly cheap looking all-plastic springer version made in China as well. If you look at the one decent image of the rifle, the ‘cheek rest’ is suspiciously similar. This would also explain the strange ridge on the top of the pistol: that’s the concealed Picatinny rail.