Securing reliable .458 SOCOM load data is essential for maximizing the devastating subsonic and supersonic capabilities of this purpose-built AR-15 big-bore cartridge.
This comprehensive guide compiles trusted .458 SOCOM reloading data to help you safely develop the ultimate heavy-hitting round for suppressed tactical operations or short-range big game hunting.
Whether you are loading 250-grain supersonic projectiles or massive 500-grain subsonic monolithic bullets, always cross-reference these published figures before charging your cases.
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.458 SOCOM Load Data
| Bullet | Bullet Weight | Powder | Published Starting Load | Published Maximum Load | Published Velocity | Barrel Length / Firearm | Source |
| Barnes TTSX | 250 gr | H110 | 33.0 gr | 36.5 gr | 1,950 – 2,150 fps | 16″ / Universal Receiver | Barnes Bullets |
| Hornady JHP | 300 gr | Lil’Gun | 27.5 gr | 30.5 gr (34,500 PSI) | 1,750 – 1,900 fps | 16″ / Universal Receiver | Hodgdon |
| Barnes TTSX | 300 gr | IMR 4198 | 34.0 gr | 38.0 gr | 1,700 – 1,850 fps | 16″ / Universal Receiver | Barnes Bullets |
| Hornady FTX | 325 gr | Accurate 1680 | 34.5 gr | 38.5 gr | 1,650 – 1,820 fps | 16″ / Universal Receiver | Western Powders |
| Cast LRNFP | 400 gr | Reloder 7 | 30.0 gr | 34.0 gr | 1,400 – 1,550 fps | 16″ / Universal Receiver | Alliant Powder |
.458 SOCOM Reloading Data
| Bullet | Bullet Weight | Powder | Published Starting Load | Published Maximum Load | Published Velocity | Barrel Length / Firearm | Source |
| Hornady InterLock | 250 gr | W296 | 34.0 gr | 37.5 gr (34,800 PSI) | 1,980 – 2,180 fps | 16″ / Universal Receiver | Hodgdon |
| Speer JHP | 300 gr | Reloder 7 | 35.0 gr | 39.0 gr | 1,750 – 1,900 fps | 16″ / Universal Receiver | Alliant Powder |
| Barnes TSX | 300 gr | H110 | 28.5 gr | 31.5 gr | 1,700 – 1,860 fps | 16″ / Universal Receiver | Barnes Bullets |
| Maker Subsonic | 500 gr | CFE BLK | 22.0 gr | 25.5 gr | 950 – 1,050 fps | 16″ / Universal Receiver | Hodgdon |
| Hornady RN | 500 gr | Accurate 1680 | 21.5 gr | 24.5 gr | 950 – 1,050 fps | 16″ / Universal Receiver | Western Powders |
Understanding the .458 SOCOM Reloading Data
Reading .458 SOCOM reloading data requires an understanding of the cartridge’s unique architecture. Developed in the early 2000s by Marty ter Weeme of Teppo Jutsu, the cartridge was designed to deliver massive kinetic energy from a standard M4/AR-15 lower receiver using unmodified GI magazines (where it single-stacks). Unlike the straight-walled .450 Bushmaster, the .458 SOCOM features a distinct bottleneck case. Because of this, the cartridge headspaces on the shoulder, meaning reloaders must properly adjust their sizing dies to avoid pushing the shoulder back too far and creating dangerous headspace issues.
.458 SOCOM Bullet Weight Reloading Data
The .458 SOCOM utilizes true .458-inch diameter rifle bullets—the exact same projectiles used in the legendary .45-70 Government. This gives reloaders an incredibly vast selection of bullet types. Supersonic load data focuses heavily on 250-grain to 350-grain bullets, which deliver optimal velocity and terminal expansion. The cartridge is also famous for its subsonic capabilities, utilizing massive 400-grain, 500-grain, and even 600-grain projectiles that retain immense momentum and kinetic energy while remaining whisper-quiet through a suppressor.
.458 SOCOM Powder Reloading Data
Powder selection for the .458 SOCOM relies entirely on fast-burning rifle propellants and magnum pistol powders. Because the cartridge operates at relatively low pressures with a large powder column, powders like Hodgdon H110, Winchester 296, and Lil’Gun are standard choices for lightweight supersonic loads. When loading heavy 400-grain to 600-grain subsonic ammunition, slower magnum pistol powders like Accurate 1680, IMR 4198, Reloder 7, and Hodgdon CFE BLK provide the necessary gas volume to cycle the AR-15 action reliably.
.458 SOCOM Bullet and Powder Combinations
Pairing the right bullet with the appropriate powder ensures maximum reliability in your specific AR-15 gas system. A 300-grain Barnes TTSX or Hornady JHP backed by a charge of H110 or Lil’Gun is the quintessential supersonic hunting combination, delivering a clean burn and excellent accuracy. If you are developing heavy subsonic ammunition, pairing a 500-grain Hornady Round Nose or specialized Maker expanding monolithic bullet with Accurate 1680 or CFE BLK ensures the bolt cycles smoothly without breaking the sound barrier.
.458 SOCOM Velocity From Published Data
Published velocity figures highlight the .458 SOCOM’s dual-purpose nature. Supersonic loads utilizing 250-grain and 300-grain bullets comfortably achieve velocities between 1,800 and 2,150 fps, matching the ballistics of modern .45-70 factory loads. Subsonic load data is intentionally tuned to keep massive 500-grain bullets hovering strictly between 950 and 1,050 fps. This specific window ensures the heavy projectiles deliver maximum kinetic energy without producing a supersonic crack.
.458 SOCOM Reloading Data by Barrel Length
Most published load data for the .458 SOCOM is gathered using a 16-inch laboratory test barrel to simulate standard AR-15 carbines. Because the cartridge utilizes very fast-burning powders, it reaches complete combustion within the first 9 to 10 inches of the bore. This makes it incredibly efficient in Short-Barreled Rifles (SBRs) featuring 10.5-inch or 12.5-inch barrels. Firing a standard supersonic load from a 10.5-inch barrel will generally only result in a minor velocity loss of 100 to 150 fps.
.458 SOCOM Energy and Ballistics
The .458 SOCOM delivers punishing kinetic energy, frequently generating between 2,300 and 2,500 foot-pounds of energy at the muzzle with supersonic loads. Its massive frontal diameter ensures devastating energy transfer upon impact. However, the heavy, flat-nosed or hollow-point bullets possess very poor ballistic coefficients. The trajectory arches steeply past 150 yards for supersonic loads and drops like a stone past 100 yards for subsonics, strictly cementing it as a short-to-medium-range tool.
.458 SOCOM Hunting Applications
The .458 SOCOM is a legendary cartridge for eradicating feral hogs and hunting whitetail deer, black bears, and even elk in dense timber. The sheer mass of the .458-caliber bullets guarantees deep penetration and massive wound channels that anchor heavy game quickly. Furthermore, its ability to reliably cycle 500-grain expanding subsonic bullets makes it one of the premier choices for suppressed, low-signature night hunting where minimizing noise pollution is a priority.
Manufacturer Data vs. Independent Testing
For many years, the .458 SOCOM existed as a wildcat without SAAMI standardization, meaning early load data was largely developed by independent testers. Today, major powder manufacturers like Hodgdon and Western Powders provide highly vetted, piezo-electric pressure-tested load data. You must always rely on modern, official manufacturer data rather than decade-old forum posts, as early experimenters frequently pushed the cartridge past safe pressure limits, which can shear AR-15 bolt lugs.
.458 SOCOM Pressure and Safety
The .458 SOCOM operates at a relatively low maximum pressure of approximately 35,000 PSI. This low pressure limit is strictly mandated because the standard AR-15 bolt face must be significantly opened up to accept the rebated rim of the massive case, reducing the structural integrity of the bolt lugs. Exceeding published maximum powder charges will increase bolt thrust to dangerous levels, leading to rapid, catastrophic failure of the AR-15 bolt carrier group.
Best Sources for .458 SOCOM Reloading Data
The most reliable sources for .458 SOCOM load data are the digital databases and printed manuals provided by major powder and bullet manufacturers who recognize the cartridge’s popularity. The Hodgdon Reloading Data Center offers extensive, free digital tables for H110, Lil’Gun, and CFE BLK. Additionally, the Barnes Reloading Manual and Western Powders’ online data hubs provide incredibly detailed, pressure-tested recipes for both lightweight supersonic and heavy subsonic projectiles.
Frequently Asked Questions
Where can I find .458 SOCOM reloading data?
You can find accurate .458 SOCOM reloading data digitally on the official Hodgdon Reloading Data Center, the Western Powders database, and in published manuals from bullet manufacturers like Barnes.
What powders are listed in published .458 SOCOM data?
Commonly listed fast-burning rifle and magnum pistol powders include H110, Winchester 296, Lil’Gun, Accurate 1680, IMR 4198, Reloder 7, and CFE BLK.
What bullet weights are covered in these tables?
These tables cover a massive spectrum of true .458-inch bullets, ranging from 250-grain and 300-grain supersonic projectiles up to 500-grain and 600-grain subsonic heavyweights.
Does barrel length affect .458 SOCOM velocity?
Yes, but the cartridge is highly efficient. Shooting from a 10.5-inch SBR rather than a 16-inch test barrel typically results in a very modest velocity loss, making it ideal for compact platforms.
Can I use standard rifle primers for .458 SOCOM?
No, the vast majority of .458 SOCOM brass (specifically Starline, which produces almost all of it) uses Large Pistol Primers, typically requiring Large Pistol Magnum primers (like the CCI 350) for reliable ignition. Always verify your specific brass primer pocket depth.
What is the difference between .458 SOCOM load data and reloading data?
There is no practical difference; both terms refer to the precise recipes of powder charges, bullet weights, and primers required to safely assemble the cartridge.
Why do published velocity figures differ between sources?
Velocity figures differ because testing facilities use varying specific test barrels, environmental conditions, brass lot capacities, and primer types during their distinct testing protocols.
Should I use the maximum published load?
You should never start with the maximum published load; always begin with the minimum recommended starting charge and carefully work up while monitoring your brass for pressure signs.
Can I use data from one bullet manufacturer for another bullet?
You should only use data specifically designed for the exact bullet profile you are loading, as variations in seating depth, bearing surface, and bullet construction drastically alter chamber pressures.
Where should I verify .458 SOCOM load data before reloading?
You should strictly verify all load data against an official, recently published manufacturer manual or a powder company’s official online database before assembling any ammunition.