Browning A-Bolt .358 WSSM

This Browning A-Bolt II Hunter is chambered in a custom caliber, the .358 WSSM wildcat. I had the build done by Mark Penrod in Indiana, who did excellent work and had come recommended for this caliber by multiple sources. The rifle is extremly accurate, and quite powerful. The cartridge's down-range energy is suitable for whitetail deer out to 400 yards and for elk to 250 yards, and the rifle has the accuracy to get me there.

Caliber:.358 WSSM (wildcat)
Barrel:Krieger 23" chrome-moly cryo-treated, 1 in 12" twist
Action:A-Bolt II, 60° bolt, push feed, 3 round magazine
Stock:Walnut
Trigger:1¾ lbs
Scope:Burris Fullfield II 3-9x40mm, Ballistic Plex reticle
Weight:

This rifle was purchased in 2010. The customization work was completed in 2011.

.358 WSSM

Indiana is a state which has not allowed deer hunting with rifles. They previously allowed only shotguns, handguns, muzzle loaders, and bows. However, in 2007 they began to allow deer hunting with pistol caliber rifles (PCR). The Indiana DNR defines pistol calibers as having a minimum bullet diameter of .357", a minimum case length of 1.160", and a maximum case length of 1.625". This was intended to allow rifles that fire cartridges like the .357 Magnum and the .44 Magnum. However, wildcatters immediately conceived of the .358 WSSM, and the DNR has gone along with these wildcats.

The .358 WSSM is based on the (ill-fated) Winchester Super Short Magnum case, necked up for a .358" bullet. The resulting cartridge duplicates or exceeds the performance of the respected .358 Winchester. Early loadings of this cartridge used a 180gr bullet, which achieves over 2600 fps. However, loads with 225gr bullets are becoming the default. With all of these loads, the terminal performance on deer has been quite impressive. This cartridge should also be suitable for elk at short ranges.

Handloading the .358 WSSM

The new barrel will be a Krieger, chrome-moly medium sporter barrel, 22" long. In addition to opening up the barrel channel, the gunsmith will square up the action and modify the feed ramp.

Zero

This rifle is currently zeroed at 100 yards for the following load: 225 gr. Sierra GameKing, 47.0 gr. VV-N135, CCI 200 primer, 2.350" COAL. The average muzzle velocity of this round is 2500 fps. The sight axis is 1.725" above the bore axis. The BC of the SGK is .384 at these velocities.

Optics

This rifle has a Burris Fullfield II 3-9x40mm scope (with Ballistic Plex reticle), and Burris rings and bases.

The Ballistic Plex reticle has marks for 100, 200, 300, 400, and 500 yards for a theoretically generic trajectory. However, in practice, there is no cartridge that exactly matches the trajectory, though many are close. Burris seems to want you to remember how much offset there is for each mark. Both the .223 WSSM and the .358 WSSM are likely to be far from matching. It seems more sensible to me to memorize yardages that actually line up with the marks, rather than even 100 yard increments. Barnes provides the actual drop at different distances that the reticle is calibrated for. I can convert that to MOA, and then I can calculate distance for each mark.

DropMOAyds fpsft-lbs
0.0 @1000.00 10022832604
 0.72 13722062431
-3.0 @2001.43 16521482305
 2.87 21520472093
-13.5 @3004.30 26019581916
 5.73 29918831772
-30 @4007.16 33618141644
 8.83 37717401512
-55 @50010.50 41616711395

Energy is at or above 1500 ft-lbs out to 381 yards.

So what I need is to calculate the distance at which the bullet will drop that much. See the ballistic calculator at BigGameInfo.com Awesome. I should probably also come up with some half-mark calculations. After 300 yards, the difference in drop is significant.

Custom Work

Barrel. Chambered .358 WSSM. Receiver trued. Feed ramp modified and polished. Trigger improvements. Barrel channel modified. Re-blued. Bedded? Dies.

The Krieger barrel is cryogenically treated. I am getting faster velocities with this gun than I expected, and I think this is part of the reason. The 180gr results are 61-78 fps faster than Hornady's .358 Winchester data, and the 225gr results are 140-159 fps faster than Sierra's .358 Winchester data.