This afternoon I loaded another 10 rounds of what is my current standard hunting load in my 257 Weatherby Magnum.  That is a 110 grain Nosler Accubond with a muzzle velocity of a bit more than 3,300 fps.  Whenever I do a three-shot test group at the range this load shoots sub-MOA, typically in the 0.6 to 0.9 MOA size.

Terminal ballistics leave nothing to be desired, even at extended ranges, and I have only recovered one projectile to date.  That one weighed 65 grains which represents close enough to 60% weight retention.

That load has delivered a series of emphatic one-shot kills and I become more fond of the rifle and the load every time I use it.  The optics assist in that greatly, as a lot of my hunting is done around dusk and dawn.  The Swarovski z6i 2.5-15×56 has excellent light gathering and razor-sharp optics.  The illuminated centre dot in the reticle makes taking a shot at an inky-black animal in poor light much easier.

100 grain .257 Nosler Partition Loads

While I was digging about in the propellant locker I found pushed into the back corner a canister of Reloader 25.  It did not have much left in it.  I weighed the remnant and did some quick sums.  There was enough to load a dozen rounds.  I figured I may as well use it up and revisit some load testing that I only skimmed over previously.

A number of reloading Gurus have stated that Reloaded 25 is one of the ideal powders for reloading the 257 Weatherby Magnum.  The Nosler Reloading Data web page also notes that, for the 100 grain projectile loading, RL25 delivered the best accuracy from all the other powders tested.

A bit more scratching about turned up the last of my 100 grain .257 Nosler Partitions; twenty-four in total.  I am a devotee of the Partitions, in any calibre.  As I said, my initial testwork with the 100 grain Partitions had not been as thorough as I would have liked.  With enough RL25 to load a dozen rounds, and 24 Partitions in hand, I set about loading a series of batches to test at the range this Wednesday.

I checked my bullet seating die.  It was set to give an OCL of 3.230 inches with my 110 grain Accubond load.  I did not want to alter that, just yet.  I took a fired case and checked what OCL the die gave for the 100 grain Partition.  It was 3.237 inches, very close to the nominal OCL of 3.209 inches in the Nosler Reloading Guide, so I accepted that setting.

Next range session I will be testing the following loads.

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For both powders, I am still 1.0 grain below the listed maximums.  I will start at the lowest charge weights and work up carefully, checking each case for pressure signs.  If there is any indication of excessive pressure I will cease the testing and take those remaining rounds home for immediate disassembly.

After next Wednesday’s range testing I will load up some varying OCL lengths at the charge weight that looked best, seeking to optimise the accuracy.  As always, it will be interesting.