.458 SOCOM Subsonic

The .458 SOCOM is exceptionally well-suited for subsonic use, making it one of the most popular large-caliber, suppressed cartridges in the AR-platform family. Developed in the early 2000s to deliver enhanced stopping power at moderate ranges, the .458 SOCOM features a large case capable of handling heavy bullets (ranging from 300 to 600+ grains) at both supersonic and subsonic velocities. When loaded below the speed of sound (~1,050 fps), it offers massive terminal energy, quiet performance, and reliable cycling—especially with properly tuned rifles.

Subsonic .458 SOCOM loads typically use bullets between 500 and 600 grains, often cast or monolithic solids, paired with fast-burning powders such as Trail Boss, IMR 4227, Vihtavuori N110, or Accurate 5744. These powders allow safe pressure levels and consistent ignition despite the cartridge’s large capacity. Trail Boss, in particular, is valued for its bulky nature, which helps fill the case and reduce powder position sensitivity—an important factor in low-charge-density subsonic loading.

A critical consideration is barrel twist rate. Most .458 SOCOM barrels feature a 1:14” or 1:18” twist, which is generally sufficient for stabilizing heavy subsonic projectiles, but twist rate must be matched to bullet length and weight for optimal accuracy. Additionally, gas system tuning and buffer weight adjustments may be necessary to ensure reliable function in semi-automatic rifles when shooting subsonic loads.

Subsonic .458 SOCOM loads are ideal for short to medium range applications (typically inside 100 yards), especially when used with suppressors, offering quiet operation and devastating terminal ballistics on game animals. Because of the large frontal diameter and retained mass of the bullets, it delivers effective energy transfer even at low velocities.