rosco well said.
The Nosler manual shows a max load in the 7mm Weatherby of 79.5 Retumbo wit 160 gr bullet for a velocity of 3189. In working with two Mashburns my buddy ran this load in his Mashburn for a velocity of 3280 fps. I backed off to 78 gr in mine with 160 AB and it ran across the screens at 3330 fps(?!).
Nothing bad happened but I suspended further testing.
I would not speculate what would have happened in a 7 Rem Mag. This underscores just how hot some 7mm Weatherby data can be.
Rummaging through my brass box I actually found that box of 7mm Rem Mag hand loads,70 H4831-160 NPT mentioned above. In the rifle in which those loads were worked up they gave right at 3100 fps with the Partition and also the 160 Bitterroot.(For those wondering the rifle shot great and case life was fine).
I recalled that I fired that same load in another 7Rem Mag, a Len Brownell custom with what I think is a 24" Douglas barrel. In that rifle the same load gave 3210 or so. That's more velocity than i like to see from a 7 Rem Mag with a 160 gr bullet.
Please note that the Nosler Manual shows 70.5 gr H4831 for the 7mm Weatherby.
Like Rosco says you can get a 7 Rem Mag close to Weatherby performance with 26" barrels,longish throats for longer seating and considerable jump to the lands,and other factors. In SOME rifles your loads may even nudge into the vicinity of Weatherby data.
But unless you very deliberately build these factors into the barrel best to stay away from Weatherby data in the Remington cartridge in most rifles.And "long throating" a 7 Rem Mag essentially makes it a wildcat.
After a whole bunch of 7 Rem Mags here's where I feel comfy with the cartridge. Used to load it hotter but no more and when I see these velocities I stop, regardless what manuals say:
160-3050 fps.
150- 3125/3150 fps.
140- 3200 +- fps.
If i want more than that, i get a bigger 7mm.
None of this is to dump on the 7 Rem Mag of course; it' s great cartridge and any game animal will wither from a bullet fired at the ballistics cited above if we pick the right one for the job.
