True that the 404 Jeffery and the 10.75X68 Mauser both use a nominally .423" bullet, I am thinking the rifles originally chambered for the 404 have a faster twist for the heavier bullets intended for the 404.
I don't have a 404 of my own anymore, but it would be interesting to get some twist rates of a few of the original rifles for comparison. I can get a measurement of my two 10.75s though.