Its as GN says, raye bored, if only near the muzzle.
In the FWIW dept. there are several dif. rifled shotgun bbls.
1) Gauge bored w/which I have zero experience aside from having seen some interesting specimens.
2) raye bored; a uniquely French approach to wood cock. note: a long time ago I used to get a rise here ref.in' it as a ortolon boring, but too many knew the real drill;-)
3) paradox guns, used to impart a spin for stabilization of slugs and balls used against dangerous game
4) diffusion type or rifled screw-in chokes
In my experience, raye bores and the rifled or diffusion type screw-in chokes all yield IC percentage patterns when using plastic wads and that would be my expectation w/the gun you describe from its rifled bbl.
Should you buy it and find otherwise, would be much interested in knowing about that.
