To the thing that lives under the bridge: at least you are contibuting to this thread in one way- proving that arrogance =ignorance.
Slugging a barrel and sizing accordingly yeilds a correct GC fit.
Good seal, good velocity, good accuracy,less leading...all frosting on the cake.
If you slug the throat and use a bullet that fills the throat as much as possibleregardless of what the rest of the barrel looks like, you'll be way ahead of the curve. A gascheck isn't goingto prevent leading if yor bullet is grossly undersized in the throat but is 'perfectly-sized' for the grooves in the barrel.