The cartridge was designed by James Howe, of Griffin and Howe. Supposedly named after Col. Townsend Whelen, a famous hunter and writer. Later evidence has come to light that suggests that the good Col. Whelen was actually involved in the development of the cartridge and tested it prior to it's final standardization. In 1987 Remington listed the .35 Whelen as a factory standard cartridge and so it is now out of the wildcat area. P.O. Ackley took the original .35 Whelen and changed it into one of his famous Ackley Improved version. The gain was 10% more capacity and a better headspace with the more distinct shoulder. The original was merely the 30-06 with the neck expanded to .35 cal. and no other changes. Which left it with a very small shoulder with only a 17deg 30' taper. Not much for a heavy bulleted cartridge. Remington and Ruger offer the caliber in their rifles but not anyone else. Only Remington manufactures the ammunition.
Performance is excellent with 200 and 250 gr bullets and it has been used to take every big game animal in North America. It also has been taken to Africa with success. The Remington pump 7600 rifle will give you very fast follow up shots and is the rifle I recommend for a hunter of big game. I have one 35 Whelen bolt action that I built from a 98 Mauser action and while the recoil is stout off the bench in the field you will not notice it as much. I plan to take it next year for elk and in that capacity it should shine. The 200 gr bullet can be pushed to 2600 fps with 3003 ft lbs of energy. The 250 gr. bullet still takes the pot with 2400 fps and 3200 ft lbs of energy. With the new slow burning powders now available you may be able to milk more fps and energy out of the cartridge while keeping pressures at safe levels.