The .243 WSSM
By Chuck Hawks
For 2003 Winchester announced a pair of new Winchester Super Short Magnum (WSSM) calibers designed for a rifle action about 1/2 inch shorter than the usual (.243 Winchester length) short action. The new .243 WSSM, the subject of this article, is one of the original WSSM calibers.
Winchester offers two deer, antelope, and black bear loads for the .243 WSSM. One of these is a Supreme load using a moly coated 95 grain Ballistic Silvertip bullet (BC .379, SD .230) at a muzzle velocity (MV) of 3250 fps and muzzle energy (ME) of 2258 ft. lbs. At 100 yards the velocity is given as 3000 fps and the energy as 1898 ft. lbs. At 200 yards the velocity is 2763 fps and the energy is 1610 ft. lbs. At 300 yards the velocity is 2538 fps and the energy is 1359 ft. lbs. The trajectory of the 95 grain Ballistic Silvertip bullet looks like this (Winchester figures): +1.2" at 100 yards, +1.1" at 150 yards, 0 at 200 yards, -2.3" at 250 yards, -5.7" at 300 yards, and -16.9" at 400 yards.
The other .243 WSSM factory load designed for hunting medium size game is a Super-X load that drives a 100 grain Power Point bullet (SD .242) at an advertised muzzle velocity of 3110 fps and muzzle energy (ME) of 2147 ft. lbs. At 100 yards the velocity is 2838 fps and the energy is 1789 ft. lbs. At 200 yards the velocity is 2583 fps and the energy is 1481 ft. lbs. At 300 yards the velocity is 2341 fps and the energy is 1217 ft. lbs. The trajectory of that load looks like this (Winchester figures): +1.4" at 100 yards, +1.3" at 150 yards, 0 at 200 yards, -2.6" at 250 yards, -6.6" at 300 yards, and -19.7" at 400 yards.
Here are some .243 WSSM specifications of interest to reloaders: bullet diameter .243", maximum COL 2.36", maximum case length 1.67".
The .243 WSSM is factory loaded close to the allowable maximum average pressure, which means that reloaders are unlikely to be able to improve much on published velocities. However, it should be possible to approximately equal the published velocities with carefully assembled maximum reloads using 55, 95, and 100 grain bullets. And, of course, reloaders can play around with 58, 65, 70, 75, 80, 85, 90, and 105 grain bullets. In the .243 WSSM I would think that 70-80 grain bullets would be most appropriate for varmints and 90-100 grain bullets appropriate for deer and other medium game animals.
The sixth edition of the Hornady Handbook of Cartridge Reloading relates that VARGET proved to be an excellent powder for varmint bullets. H4831 and RL-19 proved to be good choices for hunting weight bullets in the .243 WSSM.
The Hornady 75 grain varmint bullets can be driven to a MV of 3000 fps by 32.7 grains of VARGET, and to a MV of 3400 fps by 38.6 grains of the same powder.
Using Hornady 95-100 grain bullets, 36.8 grains of RL-19 gave a MV of 2700 fps, and 43.9 grains of RL-19 gave a MV of 3100 fps. Reformed Winchester .300WSM cases and WLR primers were used for developing these Hornady loads, and their custom Browning test rifle had a 26" barrel.
Note: A full length article about the .243 WSSM can be found on the Rifle Cartridge Page.
Copyright 2004, 2012 by Chuck Hawks. All rights reserved.