|This article needs additional citations for verification. (January 2013)|
|Place of origin||USA|
|Designer||Col. Townsend Whelen / James Howe|
|Case type||Rimless, bottleneck|
|Bullet diameter||.358 in (9.1 mm)|
|Neck diameter||.385 in (9.8 mm)|
|Shoulder diameter||.441 in (11.2 mm)|
|Base diameter||.472 in (12.0 mm)|
|Rim diameter||.473 in (12.0 mm)|
|Case length||2.494 in (63.3 mm)|
|Overall length||3.340 in (84.8 mm)|
|Primer type||Large rifle|
|Test barrel length: 24
Source(s): Accurate Powder 
The .35 Whelen is a powerful medium-bore rifle cartridge that does not require a magnum action or a magnum bolt-face. The parent of this cartridge is the .30-06 Springfield, which is necked-up to accept a bullet diameter of .358 in (9.1 mm). This cartridge is more powerful than its parent, especially in killing power on large game.
The .35 Whelen was originally developed in 1922 as a wildcat cartridge by Col. Townsend Whelen, and built by gunsmith James V. Howe (later of Griffin & Howe). At the time Colonel Townsend Whelen was the commanding officer of the Frankford Arsenal, and James V. Howe was a toolmaker in the same establishment.
The 1923 issue of American Rifleman Colonel Whelen referred to it as "the first cartridge that I designed" and in that same article stated that, "Mr. James V. Howe undertook this work of making dies, reamers, chambering tools, and of chambering the rifles, all in accordance with my design."
Suitable .358 in (9.1 mm) bullets range in weight from 150 to 300 grains (9.7 to 19.4 g). Using a 250-grain (16 g) bullet, the .35 Whelen will generate 3,500 ft·lbf (4,700 J) at the muzzle from a 24 in (61 cm) barrel.
Internet rumors state that the .35 Whelen rifle can shoot .38/.357 pistol cartridges for cheap practice. This is incorrect in that the .38/.357 has a rim that is .440" while the case measurements for the .35 Whelen are .473" at the rim (it's widest point) and .443" at its tapered smallest diameter (where the case shaft meets the shoulder). As such, the .38/.357 would slide too far into the breach due to the widest part of the .38/.357 being smaller than the smallest part of the .35 Whelen chamber until it reaches the shoulder which tapers to a diameter less than .440 (.415" at a 17 degree angle). The firing pin would then be unable to reach the primer of the .38/.357 rendering it unable to be fired. 
However, it is possible to reload .35 Whelen cartridges with the same bullets used to reload .357 magnum cartridges. Leading or bullet fragmentation within the barrel could be an issue with full power loads, so extreme care should be taken not to push the selected bullet beyond the velocity for which it is designed.
The .35 Whelen is the ballistic twin of the .350 Remington Magnum. With the correct bullet choice this cartridge is suitable for virtually all thin-skinned large and dangerous game. The European designation for this cartridge would be 9 x 63 mm; with its wide bullet selection and high muzzle energy it is in the same echelon as the venerable 9.3x62mm.
.35 Whelen next to its parent case, the .30-06 Springfield.
- .358 Winchester
- 9mm Jonson
- List of rifle cartridges
- Table of handgun and rifle cartridges
- 9 mm caliber
- .30-06 descendants
- 358 WSSM
- .35 Whelen load data
- Lee, Richard (2003). Modern Relaoding, 2nd ed.. United States of America: Richard Lee. pp. 551, 561, & 590.