Combat Rifle Reciever Change

[ThatSnipingGamer]

I remember seeing a mod at one point but i can find it anymore, is it possible that someone can replace the .308 reciever on the combat rifle with a 5.56 reciever, this would be greatly appreciated. If no one can do this, can someone link me the means of how to go about doing it myself. Thanks in advance for any and all help :)