AK Custom took a paintball grip and built a 9mm carbine pistol around it using supplies from a local hardware store.

On a Pistol Caliber Carbine group, that I am a member of, there was some discussion about the legality of this build. From the video it looks like it might be an open bolt design.

Cool design but still not legal. So thus far we have a trigger group designed specifically for open bolt operation, we have a solid 1 piece firing pin, and no hammer or striker whatsoever.

We shall see if AK Custom makes a video of it firing. If it does fire from an open bolt, he may have a visit from the ATF soon.

Edit: AK Custom responded to my question regarding if he built an open bolt firearm.

no, it is not open bolt. The firing pin catches on a sear which is released when the trigger is pulled with the bolt already being closed. Thanks