Questions were asked about the T-slot on the Prototype (J12) and whether or not it was compatible with a PE asa. Snapped some pictures this weekend to compare the two. Note that this is a prototype J12 and may not reflect any changes to the design for final production. Also I am using a OOPS asa which I assume has the same T-rail as the POPS asa.
In general, the CCM t-rail has different dimensions from the PE t-rail. The CCM rail overall is thicker and more robust making the corresponding slot larger, so the CCM asa WILL NOT fit a PE slot but a PE asa WILL fit the CCM slot. I would not recommend using the PE asa though. With the larger CCM slot, there is a lot of side-to side play and only a small bearing area on one side. One good dive into a bunker and your PE asa is gonna rip off the gun and you are gonna have to buy a new grip frame.