Every now and then, I'm tempted to call the Bunco Squad and sic 'em on the speakeasy where the gun writers hang out. "The 404 Jeffery is the parent case of the new beltless magnums." Where does this crap come from? One person says it and it becomes fact? Let's get serious…
The 404 Jeffery case essentially came from removing the rim from the 450/400 N.E. (Nitro Express) 3", and adding an extraction groove in its place. The 404 Jeffery is a little shorter, but it has the same 8-degree shoulder and rear body diameter. Since the 404 Jeffery was designed to be used in bolt-action rifles, the body was able to be made a little straighter and still offer reliable extraction characteristics. The 450/400 N.E. 3" was originally intended for use in double rifles, but has been a beautiful addition in recent years to the Ruger No. 1 cartridge lineup.
The 404 Jeffery is okay. It drives a 400-grain bullet at 2350 fps, which is just a bit shy of the 416 Remington, 416 Rigby, and 416 Ruger. Bullet diameter of the 404 is not 0.404". It's 0.423". An oddball. (The 450/400 N.E. 3" uses bullets of 0.410" - 0.411" diameter.) As far as it being the inspiration for beltless magnums, the case head of the 404 is 0.543", a little larger than the 0.534" of the U.S. beltless magnums. The body measures 0.545" versus 0.550". That takes care of the similarities. The 404 body to the shoulder measures 2.001", while the body of (for example) the 375 Remington Ultra Magnum measures 2.387". And the 8-degree shoulder of the Jeffery is very sloping compared to the 30-degree shoulder of the Ultra Mags.
American cartridge engineers already knew how big the magazine wells of rifles were, and therefore the limitations on cartridge case body diameter. Other manufacturers, including Dakota Arms Company and Lazzeroni Arms, already were using this practical maximum (for conventional bolt actions) cartridge case diameter (roughly 0.550") for many years by the time Remington introduced its Ultra Magnums and Winchester its WSMs. Lazzeroni's website states, "our proprietary cartridges have been designed from the ground up", whereas Dakota's website states, "six cartridges based on the 404 Jeffrey case", so maybe all of this started with Dakota. Other than being concerned that they didn't spell Jeffery correctly, I wonder if anyone at Dakota, including founder Don Allen as far back as 1986, ever really took a 404 Jeffery case and necked it down, blew it out, etc., to develop any of the Dakota cartridges? You know, something along the lines of Roy Weatherby developing his cartridges using the 300 H&H and 375 H&H Magnum cartridges. Anyway, just because the non-belted stuff isn't doing as well as the belted magnums that copied Weatherby's lead, it doesn't mean you have to credit it or blame it on a dissimilar British cartridge developed over 100 years ago.