DLSquide and DINK,
Sure, anybody can build a rifle with a fast-twist barrel in long-standardized cartridges. Handloaders do it quite a bit--and of course just about every Campfire member assumes everybody is a handloader.
But rifle and ammo factories have a different problem. They can't just load factory ammo for various estsblished .270 cartridges using longer, high-BC bullets, because too many non-handloaders would assume it will work in their factory .270 Winchester, .270 WSM or .270 Weatherby which have 1-10 twists. And they'd be pretty pissed when they bought the ammo, and the bullets landed sideways on targets.
The only practical way to offer factory ammo loaded with longer, high-BC bullets than typical for the caliber ("caliber" here used in the sense of the bore diameter, not the cartridge) is to introduce a new cartridge, and rifles to fire it. Doing otherwise risks creating dissatisfied customers.
