458 SOCOM Rifles, SBRs and 458 SOCOM XL Ammunition

458 SOCOM

Terminal 458: 458 SOCOM Rifles, SBRs and Subsonic Ammunition

Chattahoochee Munitions manufactures complete 458 SOCOM systems configured for XL: CM7S bolt action rifles, SBRs and pistols, including the PLACID OTB suppressed SBR and walnut-stocked models; CM10 semi-automatic rifles and SBRs on a large-frame AR10-pattern platform; all with 12.5-inch and 16-inch barrels, along with barreled actions, magazines and 650 gr XL ammunition. Start with What Is 458 SOCOM XL? or 458 SOCOM subsonic.

458 SOCOM is a .458-caliber big-bore cartridge, and its heavy bullets make it a natural fit for short-barrel subsonic shooting. A 650 gr subsonic bullet from a 12.5-inch suppressed firearm is quiet and carries about 1,473 ft-lb at the muzzle. The standard cartridge is limited by the AR15 magazine to 2.260 inches overall. The XL configuration moves past that limit: longer projectiles are seated less deeply, reclaiming usable case capacity for powder.

What Is 458 SOCOM?

458 SOCOM is a .458-caliber rifle cartridge designed in 2000 by Marty ter Weeme of Teppo Jutsu to bring big-bore power to the AR15. Its short 1.575-inch case and rebated rim fit an AR15 bolt face and magazine, which limits the loaded cartridge to 2.260 inches overall. The .458-inch bore accepts bullets from about 250 gr for supersonic hunting loads to very heavy subsonic bullets for suppressed shooting.

The cartridge is not currently standardized by SAAMI, so follow the ammunition and magazine specifications stated on each Chattahoochee Munitions product page.

458 SOCOM Specifications at a Glance

  • Designer: Marty ter Weeme, Teppo Jutsu, 2000
  • Bullet diameter: .458 inch
  • Case length: 1.575 inches, rebated rim (Chattahoochee Munitions loads use factory-new Starline brass)
  • Overall length: 2.260 inches for the AR15; XL is 2.802 inches (CM7S) and 2.790 inches (CM10)
  • Subsonic load: 650 gr Maker REX solid copper, about 1,010 fps (CM7S) and 1,012 fps (CM10) from 12.5-inch barrels, about 1,473 ft-lb at the muzzle
  • Barrel twist: 1:10 on every Chattahoochee Munitions 458 SOCOM barrel
  • Chattahoochee Munitions firearms: CM7S bolt action rifles, SBRs and pistols and CM10 semi-automatic rifles and SBRs, in 12.5-inch and 16-inch lengths, all configured for XL

What Is 458 SOCOM XL?

XL ammunition is loaded beyond the AR15 magazine limit. Chattahoochee Munitions loads a 2.035-inch, 650 gr projectile to 2.802 inches for the CM7S and 2.790 inches for the CM10. At the AR15’s 2.260 inches, that projectile would fill most of the case; at XL length it sits less deeply and reclaims usable case capacity for powder. The chamber and the case remain standard. “XL” names the projectile and the loaded ammunition, and the firearms and magazines are configured for it. Read What Is 458 SOCOM XL? for the full explanation.

CM7S Bolt Action SBRs and Pistols

CM7S Barreled Actions

CM10 Semi-Automatic Rifles and SBRs

  • 458 SOCOM Compact Rifle Select options

    CM 458 SOCOM XL

    CM10 458 SOCOM 12.5″ SBR – FDE Metallic Cerakote

     Price range: $2,398.00 through $2,488.00 Select options This product has multiple variants. The options may be chosen on the product page
  • 458 SOCOM subsonic SBR Select options

    CM 458 SOCOM XL

    CM10 458 SOCOM 12.5″ SBR – Cobalt Kinetics Green Cerakote

     Price range: $2,398.00 through $2,488.00 Select options This product has multiple variants. The options may be chosen on the product page
  • 458 SOCOM Semi Auto SBR Select options

    CM 458 SOCOM XL

    CM10 458 SOCOM 12.5″ SBR – Carbon Grey Cerakote

     Price range: $2,398.00 through $2,488.00 Select options This product has multiple variants. The options may be chosen on the product page
  • 458 SOCOM subsonic rifle Select options

    CM 458 SOCOM XL

    CM10 458 SOCOM Rifle – 16″ FDE Metallic Cerakote

     Price range: $2,398.00 through $2,488.00 Select options This product has multiple variants. The options may be chosen on the product page
  • 458 SOCOM AR10 Select options

    CM 458 SOCOM XL

    CM10 458 SOCOM Rifle – 16″ Cobalt Kinetics Green Cerakote

     Price range: $2,398.00 through $2,488.00 Select options This product has multiple variants. The options may be chosen on the product page
  • 458 SOCOM Semi Auto Rifle Select options

    CM 458 SOCOM XL

    CM10 458 SOCOM Rifle – 16″ Carbon Grey Cerakote

     Price range: $2,398.00 through $2,488.00 Select options This product has multiple variants. The options may be chosen on the product page

Magazines

Ammunition

CM Gear

458 SOCOM Subsonic: Heavy Bullets, Short Barrels, Suppressors

Short-barrel subsonic shooting is the core of Terminal 458. Below the speed of sound, energy comes from bullet weight, so the 650 gr load carries about 30 percent more energy than a 500 gr bullet at the same speed. At about 1,010 fps it stays subsonic even at 0°F. A subsonic load does its work early in the barrel, so a 12.5-inch barrel gives up little and keeps the suppressed firearm short. With subsonic ammunition, use an enclosed suppressor on both the CM7S and the CM10; the 12.5-inch CM7S is also offered with the all-titanium PLACID OTB over-the-barrel suppressor.

Read 458 SOCOM subsonic, 458 SOCOM ballistics and the 458 SOCOM suppressor guide.

458 SOCOM Bolt Action and Semi Auto

The CM7S is a Remington 700-footprint short action with a modified MDT metal AICS-pattern magazine. It makes no action noise when it fires and is offered as a 12.5-inch pistol or SBR, a 12.5-inch SBR with the PLACID OTB, 12.5-inch and 16-inch walnut-stocked models, a 16-inch rifle, and barreled actions. The CM10 is a large-frame AR10-pattern semi-automatic with a Superlative Arms adjustable gas block, an Odin Works adjustable buffer and a center-feed lower for the same magazine, offered with 12.5-inch and 16-inch barrels. Compare them in 458 SOCOM bolt action vs semi auto.

458 SOCOM Ammunition and Magazines

Chattahoochee Munitions loads the 650 gr Maker REX two ways. The bolt action load is 2.802 inches overall for the CM7S. The semi-auto load is 2.790 inches with a propellant configuration that cycles the CM10. Use each only in the platform it is made for.

Ordinary AR15 magazines do not accept XL-length ammunition. The 458 SOCOM magazine is a modified MDT metal AICS-pattern magazine configured for XL in both the CM7S and the CM10, and it is not suitable for shorter, standard loads.

458 SOCOM Guides

PLACID Suppression Guides

458 SOCOM FAQ

Who makes a 458 SOCOM bolt action rifle?

Chattahoochee Munitions manufactures the CM7S bolt action in 458 SOCOM as a 12.5-inch pistol or SBR, a 12.5-inch SBR with the PLACID OTB suppressor, a 16-inch rifle, walnut-stocked 12.5-inch and 16-inch models, and barreled actions, all configured for XL ammunition.

Is there a 458 SOCOM AR10?

Yes. Chattahoochee Munitions manufactures the CM10, a large-frame AR10-pattern semi-automatic in 458 SOCOM, with 12.5-inch and 16-inch barrels, configured for XL ammunition.

What is 458 SOCOM XL?

It is ammunition loaded beyond the AR15’s 2.260-inch limit: a 650 gr, 2.035-inch projectile loaded to 2.802 inches (CM7S) or 2.790 inches (CM10). The chamber and case are standard.

Can 458 SOCOM XL be fired in an AR15?

No. An AR15 accepts cartridges up to 2.260 inches. XL ammunition needs a short action, such as the CM7S, or an AR10-pattern rifle, such as the CM10.

Can I shoot standard 458 SOCOM ammunition in a Chattahoochee Munitions firearm?

The chamber is standard, but the magazine is configured for XL and is not suitable for shorter, standard loads.

What is the heaviest bullet for 458 SOCOM?

Chattahoochee Munitions loads a 650 gr Maker REX. At 2.035 inches long, it is loaded at XL length.

What twist rate does 458 SOCOM need for heavy bullets?

Long, heavy subsonic bullets need 1:10 or faster. Every Chattahoochee Munitions barrel in this caliber is 1:10; common AR15 barrels are 1:14.

What suppressor should I use on a 458 SOCOM?

A suppressor rated for .458 caliber. With subsonic ammunition, use an enclosed suppressor on both the CM7S and the CM10.

Who makes 458 SOCOM subsonic ammunition?

Chattahoochee Munitions manufactures 650 gr Maker REX XL subsonic ammunition, loaded separately for the CM7S bolt action and the CM10 semi-automatic.

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