Here's a pic of the throat slug from my Steyr SBS rifle in 376 Steyr (0.375" caliber). As you can see, there's a continuous taper right into the rifling. The diameter above the case is 0.382", a quarter inch up at first line it's 0.378", another quarter inch further it's 0.377" and up in the rifling the bore/groove is around 0.375" and 0.367". The top black line is maximum C.O.A.L. of 3.110" to fit in magazine.
I'd like a gas checked hunting bullet of around 300-320 grains but am unsure of the best way to achieve this. Would I be better off designing a matching taper bore rider style bullet or going with a straight LFN around 0.378" or 0.379" that's long enough to give the weight I want and engrave the nose?
I would prefer to keep the gas check mostly inside the 0.36" length case neck.
Thanks for suggestions.