Ok I looked at all the fitting up pictures and it looks like you are using inletting black to spot in the tang to the breech? This is where you should be using prussian blue, apply with q tip VERY sparingly.
Hit the high spots with a small curved tip riffler file, its slow going but will get you to a perfect precision fit joint. When that is done to satisfaction, I generally epoxy the tang to breech for inletting.
kw