Again, thanks for the thorough feedback. It's helped clear up a lot of my misconceptions---there's only so much one can learn from reading on the internet compared to real experience. Clearly the former led me to believe some marketing hype.

Great to know an adjustable gas block with a short(and by that do you mean carbine/M4 or "pistol"?)-length tube/port position is where one should set their sights.

Great to know the BCG should last longer than the barrel (though I've heard that semi-auto ones, like the Ruger, are less durable than FA---is this also true?). My dad had a bad experience with the BCG that came with his Remington R15 a couple years back, and it might have biased my expectations.

As for stabilization, I must have been misled by something I read---that a faster rate of twist with a 55-grain will be okay at shorter ranges with a 1:7", but that "wobble" will throw the bullet off MOA more than it would otherwise, as it travels further.