80 kilos is only 176 pound. Sounds like a perfect spot for an Alaskan bullet - however.

Just checked Norma's web site - right on the Alaskan and plastic tipped bullets - only up to 9.3mm - & only the Oryx design is in .375.

Since most bonded bullets have pure or almost pure lead cores, that is the one I'd try.

I would also see if the rifle would shoot a lighter bullet - like the 250gr. to 270gr. bullets- or even a 235gr.