Know whats worse than gun shop gossip Metal God? Gun shop gossip on the internet. I think the new official term for these people should be Blow-Gun-Hard's since they are blow hard's in relation to guns.
Okay so I see your point on the gas key. Sounds like a plus to me. I had been wondering why something deemed desirable for a long lasting barrel would be a minus for a long lasting BCG. So going a step further what would a chrome lined chamber offer? Any advantage?
Now as far as rifling. I have seen 1 in 9, 1 in 8, and 1 in 7. Supposedly the smaller the number the better the barrel stabilizes heavier bullets, but I have also heard that barrels can vary a lot and are more or less individuals when it comes to the bullet grains they like. Maybe a mix of both?