In fact, if I recall, the only compatible part is the pistol grip. It is a long stroke piston and uses a removable barrel. By rotating a screw, you can remove the barrel and swap with various calibers and various barrel lengths. This one was shot in 5.56mm, 300 Blackout and 7.62x39mm.
Changing out barrels and bolts is easy, the tricky part is the adjustable gas system. You balance for one round and change, you may have too little or too much gas causing failures to feed. You have to understand ammunition creates different chamber and port pressures. I have to say I enjoyed firing the 7.62x39mm round the most. The C Product Defense fed flawlessly. This is an excellent and viable weapon system.