IMR ENDURONA(R) 4166 SMOKELESS RIFLE POWDER IMR Enduron 4166 is a versatile, match-grade propellant, with the fastest burn rate in the Enduron line. It is an extruded powder with a perfect burn speed for cartridges like 308 Winchester, 7.62mm NATO, 22-250 Remington or 257 Roberts, among other cartridges. The main features of the Enduron series are copper fouling eliminator, insensitivity to temperature changes, ideal loading density and being environmentally friendly. This propellant performs comparably to Hodgdon Varget but charge weights are materially different. Mfg: Imr Powders