.358 WSSM

This is a wildcat cartridge that I will be using in a Browning A-Bolt.

Rifle: Browning A-Bolt Hunter
Forming: Forming .358 WSSM Cases

Bullet Choices

I kind of prefer lighter, faster bullets because they offer a flatter trajectory. However, the range of bullets that suit this caliber are sparse. I think my ideal loads will be the 180gr Speer Hot-Cor FN and the 225gr Sierra GameKing.

The 180gr Hornady bullet is only good for a maximum velocity of 2400 fps, so I want to avoid that. The 180gr Speer bullet is supposed to be good to 2900+ fps.

The .358 Winchester achieves 2490 fps with a 200gr bullet. The .358 WSSM easily achieves 2550 fps with a 180 grain bullet, and some people exceed 2600 fps at that weight.

Heavy Game

A cartridge using the 225gr Sierra GameKing is the load for this rifle, because it shoot so accurately. The bullet is designed for .35 Whelen velocities, which I am approaching. It is perhaps excessive for whitetail, perfect for heavier game such as elk and black bear, and it should be great on hog. A real heavy hitter. Also, my rifle really seems to like this bullet.

Bullet225gr Sierra GameKing
IMR 4320
PrimerCCI 200
CaseWinchester .25 WSSM

With N135, I appear to be getting 2600 fps or better. With that velocity, I still have 1500 ft-lbs at 400 yards.

Sierra 225gr GameKing: I didn't think I wanted to use a bullet this heavy, but my rifle really likes it. Shooting twelve rounds with a 4.4 grain spread of VV-N135, every shot landed within the two inch bull's eye. I could hunt deer with this combination today. It is a well-constructed bullet, intended for velocies such as I am getting. This is definitely the bullet I need to concentrate on.

Speer 180gr FN: The manufacturer says this bullet should perform well at 2900+ fps — which is good, because I will probably be driving it that fast. An inexpensive bullet, but not as accurate in my rifle as the SGK.

Beartooth 200gr FN: Ordered in .359" diameter, this bullet wouldn't chamber – the diameter wouldn't allow it to fit into the throat. Maybe I should check the diameter of the bullet, but I guess I have to find another solution for hog.

Hornady 180gr: The manufacturer claims this bullet is only good for a maximum velocity of 2400 fps. I can't use it for this cartridge.

VV-N135: The Hornady manual puts this powder at 2800 fps with a 180gr bullet using a max charge of 51.9 grains. However, at 47.5 grains, the velocity was almost 100 fps faster than expected. This suggests I might reach 2900 fps with this powder for 180gr bullets. It looks promising for 225 grain bullets, as well.


I have been told that a .358 WSSM case has just 1.7 grains less water capacity than a .358 Winchester. Since the WSSM is standardized at higher pressure than the .358 Winchester, the difference in case capacity is probably a wash. It should be safe for me to use .358 Winchester starting load data and work up.

sonex184, 180 gr. Hornady, 24" bbl
IMR 419844.02630
kludge, 180 gr. Hornady

Slower Powders

There is a discussion that the short, fat shape of the WSSM case leads to faster burning. In that case, a slower burning powder might be advised. I might look at the available data for .358 WSSM and then try the slower powders on the list.