Absolutely right if we're talking about barrels per se. A few years back Ross wrote up a beautiful Greener Cape gun in 30WCF/20 with oval bore in the shot barrel. Pretty versatile - rifle, shot, and slug in one gun.

That's probably the best use for the oval bore, as a Paradox. I've never played with one but there reputation indicates it can be an adventure to get them to shoot.

BTW, as indicated above H&K uses the concept in small arms, but the polygonal rifling concept is used successfully in medium caliber cannon (20-40mm) as well.

SOS