With the generosity of my local hardware store I got the rifle locked in a vice block and went about pulling the barel.
The disassembly process was pretty straight forward and the only real issue was convincing the carbon caked gas block off the original barrel.
This was the first time I had really gotten a good unobstructed look at the gas block/key. It's worth noting that the key extends a decent distance forward of the gas port in the barrel. I guess that this would result in a functionally lengthening of the gas system to somewhere between normal carbine and a midlenth, though that just a guess on my part, no idea if that extra length has any really effect on the dynamics of the gas system.
With the barrel pulled we can see the old and new barrels next to each other. The illogical profile of the government barrel becomes rather obvious next the the Green Mountain barrel, which sits somewhere between a lightweight and a tradition medium contour in profile, which I actually really like. We also see that I am going from a 16in barrel to a 14.5 inch which will have a FOSSA-556 pinned and welded for compliance.
A quick test fit for the new barrel to make sure everything lines up properly in the receiver and we are set to finish things up.