Have you tried IMR Enduron powders yet (IMR 4166, 4451, 4955, 7977, and/or 8133)? We’ve been impressed with what we’ve seen. IMR’s line of Enduron extruded powders offer excellent temp stability, reduced copper fouling, and good load density for many popular cartridges (such as .223 Rem, 6mmBR, .308 Win, .30-06, 300 WSM to name a few). Some of our Forum members have reported excellent results with IMR 4166 in the 6mmBR, Dasher, 6.5×47 Lapua and .308 Win. One member wrote: “in my 6.5×47… 4166 gives speeds and accuracy pretty much exactly the same as Varget.” And other shooters have observed reduced copper fouling with Enduron series powders, so IMR’s Enduron anti-fouling chemistry does seem to work.

IMR now offers five (5) Enduron powders: IMR 4166, IMR 4451, IMR 4955, IMR 7977, and IMR 8133. Shooters looking for good alternatives to hard-to-find extruded powders should definitely check out the Enduron line-up. Precision shooters will find an Enduron option well-suited to most popular precision cartridge types. For example, IMR 4166 is a good replacement for Hodgdon Varget (commonly used in the .223 Rem, 6mmBR and .308 Win), while IMR 4955 is a fine substitute for H4831 (favored by F-Open shooters for the .284 Win and 7mm WSM cartridges).

The Enduron Line-Up of Five Powders

IMR now offers five Enduron powders that cover a broad range of burn rates. They are suitable for a wide variety of cartridges, from small varmint cartridges all the way up to the .338 Lapua Magnum.

IMR 4166 possesses the fastest burn rate in the Enduron lineup. It is the perfect burn speed for cartridges such as .308 Win, 7.62mm NATO, 22-250 Rem and 257 Roberts. A versatile, match-grade propellant, IMR 4166 is comparable to Hodgdon® Varget.

IMR 4451 is a mid-range burn speed powder, ideally suited for cartridges such as .270 Winchester, .30-06 and 300 Winchester Short Magnum. This powder is comparable to Hodgdon H4350.

IMR 4955 is a medium burn speed powder, falling in between IMR 4451 and IMR 7977 in burn speed. It provides top performance in big game cartridges such as 25-06, 280 Remington and 300 Winchester Magnum. This powder is comparable to Hodgdon H4831.

IMR 7977 is a slower burn rate in the Enduron family. Loading density is perfect for magnums. This is a true magnum propellant yielding outstanding performance in .300 Winchester Magnum, 7mm Remington Magnum and .338 Lapua Magnum. IMR 7977 is comparable to Hodgdon H1000.

IMR 8133 IMR Enduron 8133 is the slowest burn rate in the Enduron family. Loading density is perfect for the very large magnums, including the 6.5mm and 7mm magnums. This is a true magnum propellant yielding outstanding performance in 6.5-300 Weatherby, .264 Win Mag, 28 Nosler and .300 Rem Ultra Mag, among other cartridges.

IMR Enduron Technology powders are sold in one-pound (1 lb) and eight-pound (8-lb) containers through quality retailers including Graf & Sons, Midsouth, and Powder Valley. Check frequently for current availability as these will sell out quickly after arrival. Also check your local sporting goods dealers for recent powder shipments.