This is my Mk23 carabine kit. The body is reinforced with 4 M3 threaded rods, the pistol is held in place by a 40mm long M3 screw with a 6mm tube on it, the mag catch has a pen spring and an M3 screw to keep in place, it has an M4 buffer tube adapter. If you have any question I can support you in the build.
For the build you need 4 pieces of M3 threaded roods, 7 pieces of M3 inserts and 4 M3 nuts. The pistol is hold in place by a 40mm M3 screw with a 6mm outer diameter tube on it (I've used carbon fiber tube) in the Front body 4 insets are for the threaded roods, at the back end the nuts are tightening the whole body, it makes easier to glue it, and it offeres extra strength to the body.
If you like this model, feel free to support me :) If I get enough support, I will design an MRAD stock for the VSR10/SSG10 sniper ;) or/and for the AS-01 striker.