I'm imagining a .45 caliber rifle cartridge, something capable of driving a spitzered 300 grain bullet at about 1900 FPS to produce muzzle energy comparable to say a .308 Winchester. It would be something like a .45-70 updated for better pressures and pointed tip bullets. It seems to me all the other .40 and over rifle rounds are either round-nose or overpowered rounds designed for big game. With all the niche rifle rounds out there, why isn't there one that combines the hitting power of a larger bullet with the ballistic performance of something like .308?