From FireArm Blog:

The gun shoots BBs at 600 fps. If it was able to achieve this with even the heaviest .22 BBs it would only generate just over 12 ft/lbs of energy. Before you get too excited about defending your castle with this legal-to-own-without-paperwork machine gun, it is defiantly not a toy but is not nearly powerful enough for self defense. The GSMG is currently a prototype and the final product will sell for around US$350.

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