You fellers are probably right about the Milek load. He uses 29.0 of N200 and the Sierra 125-grain spitzer in an antelope hunt he describes on Page 36 in the chapter on Open Country Hunting in "A Complete Guide to Handgun Hunting," published by Guns and Ammo in 1979. He also lists this as the only 125-grain Sierra load in a chart on page 32 of this publication that shows his loads for .308 X 1.5, .30-30 and a number of other rounds. Obviously, this "book" was published years after the initial development work on the .30 Herrett was complete, and it would not have been the original load.
My apologies.
That said, I nearly wore out my copy of this book, and put together a 10-inch barrelled .30 Herrett with Leupold M8-2X scope nearly 25 years ago. It was my first wildcat and I sure loved the rig, although I never got close enough to a mule deer to have a shot with it.
Still have a soft spot for that stubby but efficient little cartridge, though.