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The standard AR-15 chambered in 5.56 NATO is truly America’s rifle and is a symbol of American ingenuity and freedom. Although the 5.56 NATO has proven itself in the jungles of Vietnam and deserts of Iraq, some gun owners wanted something more…

They wanted more stopping power, better terminal ballistics, and a rifle cartridge that could be used for both home defense and big game hunting.

The 458 SOCOM cartridge is the answer that these gun owners were looking for, as its heavier bullets can deliver bone-crushing kinetic energy that can stop feral hogs or whitetail in their tracks.

However, is investing in a big bore 458 SOCOM upper receiver really worth it? Or is it better to stick with the AR-15 platform mainstay, the 5.56 NATO?

In this article we will help you answer these questions and more as we compare the 458 vs 556.

what is the difference between 5.56 and 458 SOCOM?

The primary differences between 458 SOCOM vs 556 is bullet diameter each cartridge fires and the intended engagement ranges. The 458 SOCOM fires a 0.458” diameter bullet that is intended for close-range engagements while the 5.56 fires a 0.224” diameter bullet that excels at long-range shots.

 

 

Muzzle Velocity and Kinetic Energy

When it comes to muzzle velocity, there are only a handful of rounds that are faster than the 5.56 NATO. However, the 5.56 cannot keep up with the 458 SOCOM in terms of muzzle energy.

For this example, we will compare the Hornady Frontier 55 gr FMJ (M193 clone) for 5.56 and the SBR Ammunition 300 gr Barnes TTSX load for 458 SOCOM.

At the muzzle, the 5.56 round is blazing down range at 3,240 fps compared to 1,835 fps for the 458 bullet. Although this is only one example, essentially every 5.56 factory load will have a higher muzzle velocity than the 458 SOCOM since the 5.56 is firing lighter bullets.

However fast the 5.56 bullet might be, the 458 SOCOM is using a considerably heavier bullet that carries a lot more muzzle energy. At the muzzle, the 458 SOCOM bullet delivers a whopping 2,243 ft-lbs of kinetic energy compared to 1,282 ft-lbs for the 5.56.

Although the 458 SOCOM round has almost double the kinetic energy at the muzzle, the round quickly loses fps and ft-lbs of energy as it travels downrange due to its bullet design. By 300 yards the 300 grain bullet has gone subsonic and by 600 yards it carries around 500 ft-lbs of energy. To put that into perspective, that is still more than a 45 ACP +P round has at the muzzle, but it illustrates the primary difference between 5.56 and 458 SOCOM. In contrast, the 5.56 55 grain bullet goes subsonic around the 700-yard marker.

The 458 SOCOM was clearly designed for close-range shots at self-defense distances where it can use its massive kinetic energy advantage to devastating effect. While the 5.56 had long-range shooting and marksmanship in mind for longer engagement distances.

There’s a lot of data at the source.