Shawnee KS, IMR Legendary Powders has created a line of sophisticated extruded powders utilizing Enduron Technology. Their fine, extruded propellant features a unique copper fouling eliminator, insensitivity to temperature changes, ideal loading density and is environmentally friendly. IMR 4166 is the first in a series of Enduron propellants. It's a perfect burn speed for cartridges like the 308 Win/7.62mm NATO, 22-250 Remington, 257 Roberts and dozens more. Positively, a versatile, match grade propellant.