I wish you would tell that to my experimental SMLE sporter chambered for an approximation of the .375 JDJ cartridge. It shoots 270-grainers fine at about 2150, but the 285-gr Grand Slams I picked up at a close-out sale, at 2100fps, shoot 1-inch 3-shot groups at 50m (ghost-ring peep) but are sideways with 2-foot groups at 100m.

BTW the rifle is a marvellous scrub-gun, 7 lb, blonde epoxy stock-finish, brass buttplate, Yuck!! ...but a perfect knock-about or loaner. It has taken 3 buffalo and numerous big Territory boars with the 270-grain Hornady spire-point. Total cost AU$250! ...but that's another story!