I've used a few Montana barrels. They are button rifled and are a well finished barrel and properly stress releived. However, I've yet to see a straight one. The curvature is not so great as to seriously affect accuracy, in fact all have been very accurate. It is enough to make set up and chambering somewhat more difficult if one wants to produce a perfectly straight and concentric chamber. All in all, they are a fairly good value.
I am unable to comment on the work from Bits of Pieces since I've not looked at any examples and probably wouldn't comment if I had! Regards, Bill.