i'm still debating either the 100 grain TTSX or the 120 grain partition
September 9, 2009, 08:05 PM
The .257 Wby is a magnum cartridge, to be sure, the SAMMI pressure spec is 55,000 cup. Slightly less than the non-magnum .25-06 at 56,000 cup.
The case holds, on average, 84 grains of water. That’s a good heapin’ helpin' in my book. But, in comparison, a .300 Win Mag will hold 89 grs.
Pressure and capacity wise, it seems pretty middle-of-the-road, as magnums go, by today’s standards, at first glance. But…..
What sets this cartridge apart is what’s called Relative Capacity. RC is a function of case capacity divided by bore area. It’s a key concept in cartridge performance predictions and optimal powder selection.
Dude, Relative Capacity for the .257 Wby is off the friggin’ hook!! Right up there with the .50 BMG. Take heed. Slamfire1 ain’t a kiddin’.
So, given what we know about the case, it’s capacity, length, COAL, the OP’s desire to use a 100 or 120 gr bullet…..
Mirror, mirror, on the wall. What’s the best powder of them all?
Well, I don’t have a magic mirror. But I do have my own Powley Computer (Powley-esque, really). Punch it all the numbers, just takes a second (it’s a spreadsheet, so it’s just a quick cut & paste, enter the bullet weight & length, COAL looks good, a little tweak to the load density…..).
Yep. Big surprise here. You gonna need a really, really, REALLY, slow powder. I’m gonna recommend you start with RL-22 for the 100 gr bullets, and H870 for anything heavier.
September 9, 2009, 09:06 PM
Here's the load I use.
If you start with a good bullet and appropriate powder, you should be able to complete load workup in way less than 200 rounds. A 257 Weatherby Magnum barrel should be good for a minimum of 2 or 3 thousand rounds.
September 9, 2009, 09:35 PM
If I'm not mistaken, Grumulkin's COAL exceeds SAMMI spec by 45 thousanths. Could be an issue in some chamberings.
September 9, 2009, 09:48 PM
Yea, it probably does exceed SAMMI specs which means nothing as long as the round will feed reliably from the magazine, the bullet is not jammed up against the lands and enough of the bullet is in the case to hold it securely. The length might have to be shorter in some firearms.
September 9, 2009, 10:34 PM
Grumulkin thats a great group.I am getting about 1/2 to 5/8 th inch with the factory 100 grain spire points.Id use those if knew they would stay together on a deer
September 11, 2009, 08:00 AM
Used the factory 100 grain spire points when first got 257 wby (Japanese version), and they worked just fine on deer. All the 100 grain spire points used in the factory cartridges had a measuradbly wider dia , than the 100 grain spirepoints purchased seperately. Have used Barnes bullets since started handloading for it.
RL-22 and Fed mag primers work excellent in 257 wby, and never was tempted to try anything else. Doesn't mean other very slow powders wouldn't work as well.
If the copper fouling is allowed to build up, some might think the barrel is "shot out". Got a pretty good deal on mine that way. When new, the accuracy dropped off considerable after 20 rounds. If the barrel never gets broke in, the problem is worse. Am not putting 20 rounds down range rapidly.
Can't seat a bullet out far enough to touch the lands on the one owned, and as pointed out the mag well is the limiting factor on COL.
Brass is expensive, maybe good for 3-4 full bore loads. Maybe more if ya download just a tad.
September 11, 2009, 08:09 AM
thank you zeke Can I ask at what ranges you shot the deer with the 100 grain spire points.They shoot wonderful in my rifle.Im just concerned about blowing up.Where I shoot I am shooting into a old log,and they look pretty explosive.
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