The 100gr Weatherby ammo w/100gr Norma Soft point is the least expensive. It runs ~38.00/box. Second least expensive ammo is Weatherby w/100gr Hornady PtSpt. Either will run 3,450fps from 24"bbl, 3,500fps from 26"bbl. Either is sub-moa from my Weatherby Vanguard.
Factory Ammo for this cartridge isn't cheap, but all is good.
I've only shot one box of factory ammo, with the Norma bullet. I bought it because it was cheaper than unprimed, empty Weatherby brass. Go figure !!!
I normally use 100gr Hornady PtSpt's as I bought a large quantity of "blems" several years back. Only thing wrong with them is that they have some stains on jacket that weren't polished out by Hornady, so were "rejects".
They shoot accurately and perform perfectly on deer.
I use primarily RL25 at 74.0gr for 3,650fps from my rifle. I use a +1.0" at 100yds as this gives me a point-blank range of nearly 300yds. A LOOONG shot in my neck of the woods.
Sight in 1.1" high at 100yds for 200yd zero. This will put you ~4" low at 300 and 12" low at 400yds.
+2.5" at 100yds will give you +3" at 200yds, zero at 300yds and ~10" low at 400yds. Essentially point and click to 350yds.
Other powders I've used with excellent results are:
IMR-7828 @ 72.0gr for 3,600fps
IMR-4350 @ 63.5gr for 3,450fps (duplicates factory ammo)
H-4350 @ 64.0gr for 3,550fps (very accurate my rifle)
All above loads used Fed. 215primers and Weatherby cases.
You can re-form 7mmRemMag brass, and will end up ~0.15" shorter than factory brass, but otherwise entirely useable. It will require fire-forming to blow out shoulder to full dimensions. Reformed brass or brass from other venders such as Federal, Remington will be 2-3gr lower in capacity than the Norma mfg. Weatherby brass. As such, they will require reducing charges 1-2gr. (See Speer #14 manual. This explains the descrepancy from other data souces.).
with a 120gr Nosler Partition or Swift 120gr A-frame bullet, it's suitable for anything in N.America except for brown/grizzly bear. For those, I'd use something a good bit bigger.
The .257wbymag is one of my favorite cartridges....
