Though I cannot currently give a source for either I have seen references of straight grooves being applied to a shotgun bbl for the purpose of "Eliminating Spin" & thus to improve the pattern (read that a closer one) & also rifling (spiral) for the purpose of increasing spin to scatter the pattern. The later I seem to recall being mentioned by Roger Barlow in reference to French guns.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra