257 Wby Magnum loads in resized 7mm Rem Mag brass- Starting loads

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pacobillie

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I recently acquired a Weatherby Vanguard S2 rifle chambered for 257 Weatherby Magnum.

In view of the high cost of 257 Wby brass, I resized some 7mm Rem Mag brass in a FL 257 Wby sizing die, after annealing the neck and shoulder of the cases. Surprisingly, the cases now feature a nice double radius shoulder typical of Weatherby cartridges, and it does not look like fire-forming will be required.


I am now ready to load some rounds and shoot them I have IMR7828SSc on hand.

Here is my concern: I read that Weatherby/Norma cases weigh 211 grains on average. See: http://www.sportingshooter.com.au/news/reloading-the-257-weatherby-magnum

If that statement is correct, it makes a significant difference. Indeed, my resized Hornady 7mm Mag brass weighs 262 grains, which means it is a lot thicker and has a lot less internal volume than Weatherby brass.

Published Max load for IMR7828 is 71 grains with a 110 grain bullet. How much below that would you start to be on the safe side in my circumstances? Please state whether you have actual experience with what you suggest.
 
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Use published start data and work up, same as any new cartridge loading process. Your start should be the same, your max will be lower.
You can't drop slow powders too much or you can run into issues.
Other issue using 7mm brass is you get a considerably shorter neck then the typical 257 brass, might not be the best idea in the long run, Hornady 257 brass is not expensive.
 
Hitzy said:
Use published start data and work up, same as any new cartridge loading process. Your start should be the same, your max will be lower.
You can't drop slow powders too much or you can run into issues.
Other issue using 7mm brass is you get a considerably shorter neck then the typical 257 brass, might not be the best idea in the long run, Hornady 257 brass is not expensive.
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FYI, this is a load from the Nosler website and handbook, and the published starting load is 67 grains of IMR7828
 
Start there...use a chrony so you know the velocity and go from there. Chrony is your best tool for determining pressure. Heavy brass won't show signs as fast, I have some PRVI 7mm that weighs the same...260gr or so, the Nos brass I have weighs 218gr. You lose about 1gr of volume per 11gr of brass so your start loads may be close to max velocity already, or it may not, only way to check is with a chrony.
 
At the website below it shows the case capacity to be 84 grains of H2O for both the 7mm mag and 257 Wby mag.

Cartridge Case Capacities
http://kwk.us/cases.html

And below is from the link you posted for "Reloading the .257 Weatherby Magnum".

"In fact, there is very little difference in capacity between the .257, .270 and 7mm Weatherby cases and the .264 Winchester and 7mm Remington Magnum cases."


Bottom line, as Hitzy ststed above just make a workup load starting at the suggested start load and work up.
 
As a rule for every 10 grs heavier a case is the capacity is reduced by 1 gr of powder My 257 never saw any Wby brass for years. Start loads 3or 4 grs less than wby cases and work up watching for signs of excess pressure
 
I shoot 7mm Weatherby Magnum using 7mm Remington Magnum brass that I full-length resized, then fire-formed using 150gr SP with Trailboss (70% of full case measured to the bottom of the bullet). I now use the reformed brass with the starting load of 66gr of IMR7828 with my 150gr SP. I have not tried to load any more than that in these cases as they are accurate and already kicks. Like you, I note that the 7mm Remington bass is much heavier than my Weatherby brass, even though the neck is noticeably shorter.
 
Dogleg said:
Start at the Starting load and quit when the gun tells you to.
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My fear is that the published starting load (67 grains) may be on the high side, given the difference in brass thickness (less internal volume). As one poster wrote, it may be close to max for that brass.
 
pacobillie said:
My fear is that the published starting load (67 grains) may be on the high side, given the difference in brass thickness (less internal volume). As one poster wrote, it may be close to max for that brass.
Click to expand...


If you’re really scared load a few extras a couple or three grains under the staring load. Just do one of each, for peace of mind. Shoot the lowest and if nothing falls off do the next one.

I’ve used a lot of Rem 7 Rem brass for the .257 and the load ends up being the same as those in Weatherby brass.
 
To close the loop, here are the results.

Accuracy load with 110 gr ELD-x is 68 grains imr 7828 ssc. It also appears to be max load, and is 3 grains below published max load for Weatherby brass. Velocity ia about 3455 fps (3 shot average)

Group size is just below 0.5 in at 110 yards. The accuracy node is very narrow. Groups open up and velocities jump up significantly at 68.5 grains. Also got some loose primer pockets at 68.5 .
On the low side, group size only tightened up starting at 67.5 grains. Hence, my claim that the accuracy node is quite narrow.

Rifle is a weatherby Vanguard with factory synthetic stock. Unbedded.
 
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pacobillie said:
To close the loop, here are the results.

Accuracy load with 110 gr ELD-x is 68 grains imr 7828 ssc. It also appears to be max load, and is 3 grains below published max load for Weatherby brass. Velocity ia about 3455 fps (3 shot average)

Group size is just below 0.5 in at 110 yards. The accuracy node is very narrow. Groups open up and velocities jump up significantly at 68.5 grains. Also got some loose primer pockets at 68.5 .
On the low side, group size only tightened up starting at 67.5 grains. Hence, my claim that the accuracy node is quite narrow.

Rifle is a weatherby Vanguard with factory synthetic stock. Unbedded.
Click to expand...

Looks like you're getting your speed so I wouldn't sweat the charge compared to the book. 24" barrel?
 
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