I now have plenty of 5.45x39 ammo. What parts do I need? If I order a Spike's AR15 mid length in 5.56, what other parts will I need to shoot 5.45? I see Spike's sells a part for shooting 5.45. Is that all I need or do I need a different barrel as well? On a related note I saw you can switch a single part and shoot .22lr out of it in a youtube video. Is this true?