Yeah, Straight Rifling for sure & I have been told the teem >>Hair Rifling<<, but I do not know it's true meaning nor if the method varied from straight to concentric.

I think the scattergun tubes have been lightly honed.

Indeed, there isn't a traditional mechanism to stabilize a solid projectile but the striations might have been for tossing large shot. Maybe a pattern effort on the Biks might shed some light¿

Serbus,

Raimey
rse