Short action magnum cartridges, are by name, supposed to be designed for a short action rifle! For whatever reason, the rifle manufacturers, cartridge designers, and bullet manufacturers, are not on the same page. The SHERMAN SHORT were designed to optimize performance in a short action rifle with the latest, heavy for caliber, high b.c. bullets, and they do just that!
The picture above clearly shows why this is true. The 7 SAUM (L) and 7 SS (R) are both loaded to 2.920’” with a 180 Berger, which is just off the lands in the SS design. Its quite obvious that the bullet is positioned in the SS case, with the boat tail/body junction of the bullet, positioned correctly in the neck to maximize case capacity, while the SAUM has a considerable amount of capacity taken by the bullet.The above illustration of the 7 SS is also true of the 6.5 SS, and the larger bores as well. In other words, unless the SAUM is single fed with the bullet seated out, you are leaving performance on the table!
This shows up clearly in field tests between the two designs. First of all, due to the SS having less body taper (and 40 degree shoulder) than the SAUM, the case capacity of the two are nearly identical even though the overall length of the SS is much shorter in the critical body area, and the neck/shoulder junction, which determines throat length for proper bullet positioning.
Secondly, the shorter powder column and 40 degree shoulder facilitate more efficient, uniform combustion. The longer neck on the SS, in conjunction with the sharp shoulder angle, helps confine the flame point inside the neck and, many believe, reduces throat erosion.
The low body taper and 40 degree shoulder also helps resist case stretching for longer case life, and the low taper reduces bolt thrust which allows running a little more pressure than with the same parent case with less taper.
All of these things combined add up to the SHERMAN SHORT family of cartridges outperforming other magnum designs.
With head stamped brass now coming available, why would one not choose the SHERMAN SHORT options!
Learn more about the different caliber offering in this versatile family of short magnum cartridges.