then the .577 Nitro Express in 1900, which used modern metal jacketed and solid bullets pushed by more modern smokeless powders. It was not until the parallel developments of jacketed projectiles, closely followed by smokeless powders in the late 19th century, that dangerous game could be taken with near 100% certainty. Nitro Express rifles The Nitro Express line (c.1895), so named because the composition of the early smokeless powders such as Poudre B, ballistite and cordite, were the first of the new order of elephant guns. With smaller metal-jacketed projectiles ranging from .400 to .620 inch caliber and velocities around they possessed vastly improved trajectory and penetration over their black powder forebears. Within a few years the mighty bore guns of the previous era largely disappeared from the gamefields. The safari heyday of the early 20th century "nitro era" records much literature on such calibers as the .577 Nitro Express, .375 H&H Magnum, .416 Rigby, .404 Jeffery, .505 Gibbs, .450 Nitro Express, and .470 Nitro Express. These rifles came out in single shot, bolt action, and double rifle configurations and continued to be used until ivory hunting died off in the mid-20th century. Thereafter, they largely switched roles to tools for game wardens and as back-up firearms for professional hunters guiding international hunters. The American gun market produced several famous dangerous game cartridges around this time, such as the .458 Winchester Magnum, .378 Weatherby Magnum and .460 Weatherby Magnum and many of these were "wildcatted" (to modify an existing case and rifle to fire a different caliber bullet). The rest of the old Nitro express calibers had faded into obscurity until a resurgence in safari hunting came about in the 1970s and 1980s. This prompted a new boom in elephant gun development and calibers such as the .416 Weatherby Magnum and .416 Remington Magnum arrived in factory offerings. The late 1980s and 1990s produced the .700 Nitro Express and the new brass manufacturers allowed even more powerful elephant guns such as the .585 Nyati by Ross Seyfried, .577 Tyrannosaur by Colonel Art Alphin and .585 Gehringer by Karl Gehringer to be made by wildcatters. The .600 Overkill made by Rob Garnick represents the greatest power available from a standard hunting action. Other wildcats based on the heavy machine gun .50 BMG and similar anti-materiel rounds have been devised which are much more powerful, though they are not generally considered useful