Your final words about "blanks to be filled in" is the big truth we all have to keep in mind. I think you are also correct in your feelings about shallow MicroGroove barrels. But I have to disagree with your theory regarding Pope and gain twist. An incident as B A described would produce one area of "stretched" rifling followed by a return to a shorter rifling. The gain twist starts out long and spirals shorter with each revolution, thereby sealing any gas leakage, at least in theory. At least that's the way I see it, but I'm sure Joe will tell me I'm wrong, and since I can't prove otherwise, I won't argue with him. There, Joe, saved you a post...Originally Posted by Bullshop