IMR 4166 with ENDURON Technology Smokeless Powder 8 Lbs, this fine, extruded propellant is the first in the series of Enduron Technology powders. The main features of the Enduron series are copper fouling eliminator, insensitivity to temperature changes, ideal loading density and being environmentally friendly. IMR 4166 is the 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. Grain shape is extruded (stick).IMR 4166 with ENDURON Technology Smokeless Powder 8 Lbs available in stock for sale.