New Powders - New Loads
by Tim Banse
Reloading the .303 British with IMR's new 4166 and 4451 Enduron powders.
In 2015 IMR introduced three new Enduron powders, more particularly, IMR 4166, IMR 4451, and IMR 7977. All three of these new propellants feature small kernels for easy metering and a built-in copper fouling eliminator. Morever, Enduron powders are not sensitive to temperature changes. But here lies the real eyebrow raiser: according to Hodgdon, its IMR 4166 is nothing less than a "versatile, match grade propellant".
With that preface in mind we present load data for two of the three powders in a variety of bullet weights and loads. And we've fused into that load table some information on the ubiquitous .303 Mark 7 military load as well as factory Remington 174 and 180 grain weights, which lends perspective on relative velocity. Also for perspective's sake, we've included load data for IMR 3031. That's for the simple reason that venerable Improved Military Rifle 3031 was the first propellant after Cordite to be loaded in the .303 British.
|Powder||Bullet Weight||Bullet Diameter||COL||Primer||Charge (grains)||Velocity (fps)||Pressure||Charge (grains)||Velocity
|IMR 4166||125||.311||2.915||Remington Large Rifle||44.2||2,739||37,500||47.2||2,907||43,000|
|IMR 4166||150||.312||2.995||Remington Large Rifle||39.9||2,477||36,400||43.9||2,693||43,600|
|IMR 3031||150||.312||2.995||41||2,632||46,100 PSI|
|Remington Factory||FMJ 174||.311||3.075||2,475|
|IMR 4166||174||.311||3.075||Remington Large Rifle||2,475|
|IMR 4451||174||.311||3.075||Remington Large Rifle||45.6||2,397||36,800||49.6C||2,590||43,300|
|Military Mark VII load||174 FMJ||.311||3.075||2,440||45,000 CUP
|Remington Factory||Core Lokt 180||.311||3.075||2,460|
|IMR 3031||180||.311||3.075||38.3||2,341||46,500 PSI|
|IMR 4166||Speer 180 Hot-Core||.311||3.075||Remington Large Rifle||37.5||2,265||34,900||40.8||2,453||42,300|
|IMR 4451||Speer 180 Hot-Core||.311||3.075||Remington Large Rifle||45.2||2,361||37,300||49.2C||2,556||43,900>|