First off, I'm one of those guys that never leaves well enough alone. I haven't even received my upper yet and I'm already thinking about what I'm wanting to change. I'm playing with the idea of converting my 5.56 RRA upper to 300 BLK. I've heard that all you need to convert is to change the barrels. The problem I am running into is my upper has a mid length gas system. My question is, would it be relatively easy to change to a carbine gas system when I change barrels? What all is involved with the whole process? What would be the cost to have someone do this for me if I supply the parts?