In my collection, I have a Westley Richards double, about same vintage, in same caliber. Also, I have several other British rifles in same caliber, some hammer doubles, but most hammerless; some regulated for 270 grain bullets; some regulated for 300 grain bullets. The best accuracy and regulation I ever got, for 270 grain bullet rifles, was using 40 to 43 grains of 4895, with dacron filler.