Command Arms Accessories at SHOT Show had a prototype kit to convert a Glock pistol into a carbine on display. The kit is called the PTP. I have not idea what it stands for. It is a clever design that prevents any chance of the slide hitting the operator on recoil.

Photos Copyright Remigiusz Wilk (REMOV). Used with permission.

It is not quite the carbine glock fanboys have been waiting for 😉