257 Weatherby COL
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On my first 257 on a Mark V I loaded for magazine length minus a bit of rattle room for function with a 100 grain NBT. As it happened, that worked out to 3.333" and shot so freakishly well that I decided that the all 3s COL had some magical property and left it alone. 
With only one bullet exception that I can remember off the top of my head and over many different bullets and different rifles I just never bothered setting the seater again. Always seems to work, but magic is like that.
With only one bullet exception that I can remember off the top of my head and over many different bullets and different rifles I just never bothered setting the seater again. Always seems to work, but magic is like that.
On my first 257 on a Mark V I loaded for magazine length minus a bit of rattle room for function with a 100 grain NBT. As it happened, that worked out to 3.333" and shot so freakishly well that I decided that the all 3s COL had some magical property and left it alone.
With only one bullet exception that I can remember off the top of my head and over many different bullets and different rifles I just never bothered setting the seater again. Always seems to work, but magic is like that.
Thanks Dogleg! I'm just trying to conduct some calculations. With your 3.333" COL minus 3.209" (Nosler Manual) equals .124" closer to the lands. The 257 Wby. free bore is .378" minus .124" equals .254 jump. I have a short throated 257 Wby. which I recently had built and trying to figure starting powder load and jump with the Nosler 110 gr. Accubond. So far a 0.50 jump and starting 5 grains "below" Noslers minimal for IMR-4350 and IMR-7828 and work-up .5 grains to 2 grains below minimum.
Don't try to calculate the jump; just measure it. The .378" figure is arbitrary and changes with the exact bullet. Working up is wise of course; but I wouldn't burn up a bunch of powder at 5 grains under starting loads. I'd just do one at 5 under, one at 4 under and so on up to the book max then just shoot them in order until the gun tells you to quit at your own working maximum. Write the charge right on the cartridge cases so you don't get mixed up and to allow for a bit of a review later. The results might; and probably will surprise you.
I've got a shortened throat 270 Weatherby built with a heavy Gaillard barrel and 3.800" mag box. Likely due to the shortened throat it'll send the cheapest Weatherby 130 grain factory ammo at 3700 fps with nothing that anyone would describe as pressure signs. (Except the velocity) With the long box I can load most bullets to the lands and ended up right on the Nosler book maximums anyway. Oddly; it didn't shoot well at that length so I ended up seating them deeper until it woke up at a .180" off. Turns out it liked the jump.
If I had placed bets on the outcome I would have lost money on every aspect.
I've got a shortened throat 270 Weatherby built with a heavy Gaillard barrel and 3.800" mag box. Likely due to the shortened throat it'll send the cheapest Weatherby 130 grain factory ammo at 3700 fps with nothing that anyone would describe as pressure signs. (Except the velocity) With the long box I can load most bullets to the lands and ended up right on the Nosler book maximums anyway. Oddly; it didn't shoot well at that length so I ended up seating them deeper until it woke up at a .180" off. Turns out it liked the jump.
If I had placed bets on the outcome I would have lost money on every aspect.
