No reason that the .40 whelen won't work if the reamer is spec'd properly. Big Bore Rifles and Cartridges covers it I think. Ken Howell also does in his manual of cartridge conversions.
I went a slightly different route. I built a .44 Whelen, the .429 express. It is a .30-06 blown out straight to .429 caliber, and headspaces on the mouth. It works flawlessly in my mauser. It will push a 300 grain bullet to 2400 fps, with Powley computer estimating 55,000 psi, similar to the .270.
This is a real cheap wildcat. Chamber it with the .444 marlin reamer. I lengthened my chamber with a 7/16" chucking reamer, which squares up the chamber end some to help headspace cleaner. Fireform the brass with 8 grains of red dot and a case full of cream of wheat. Use .444 marlin dies to load it. With a slight chamfer at the chamber end of the barrel, it feeds in my mauser without modification.
I invented this independently, and then found out that Ken Howell had done the same. Still later, I found that Elmer Keith had done it a long time ago. It's not a new wildcat. Only real drawback is the lack of good .44 caliber bullets.
dave
