458 SOCOM Subsonic Ammo — 650gr Maker REX 458 SOCOM XL

Chattahoochee Munitions 458 SOCOM Subsonic Ammo combines the extreme projectile weight of the 650-grain Maker REX with the additional cartridge overall length available in a SOCOM XL-compatible bolt-action platform. Loaded in factory-new Starline brass, this ammunition is purpose-built for heavy-projectile subsonic applications.

The 650gr Maker REX is an exceptionally long .458-caliber projectile, measuring 2.035 inches in length. Chattahoochee Munitions loads this ammunition to an overall cartridge length of 2.802 inches, moving beyond the cartridge-length limitations of a conventional AR-15 magazine.

This ammunition uses Chattahoochee Munitions’ SOCOM XL extended-OAL configuration, but it does not require a different chamber or cartridge case. The chamber remains .458 SOCOM. SOCOM XL provides additional usable cartridge overall length to better accommodate exceptionally long projectiles such as the 650gr Maker REX.

650gr Maker REX Expanding Projectile

The 650gr Maker REX expanding projectile is a precision CNC-machined, lead-free, solid-copper projectile engineered for expansion within a specified velocity range. According to Maker, REX projectiles are designed for substantial expansion while maintaining nearly all of their original weight.

At 650 grains, this projectile provides exceptional mass for 458 SOCOM Subsonic Ammo, while its solid-copper construction and expanding design make it purpose-built for terminal performance at subsonic velocities.

Maker REX Projectile Specifications

• Diameter: .458″
• Projectile Weight: 650 grains
• Projectile Length: 2.035″
• Construction: CNC-machined solid copper
• Lead Free: Yes
• Design: REX expanding
• Sectional Density: .443
• Ballistic Coefficient: .44 G1
• Recommended Barrel Twist: 1:10

458 SOCOM Subsonic Ammo Tested at 1,010 FPS

Chattahoochee Munitions chronograph testing produced an average muzzle velocity of 1,010 fps across a 10-shot sample fired from a 12.5-inch barrel.

At that measured average velocity, the 650gr projectile produces a calculated 1,473 ft-lbs of muzzle energy.

Rather than relying on generic .458 SOCOM ballistic figures, the ballistic information presented here is based on the actual 650gr Maker REX projectile specifications and Chattahoochee Munitions chronograph testing.

650gr 458 SOCOM Subsonic Ballistics

The following trajectory figures are calculated using the 1,010 fps CM-measured average muzzle velocity, a .44 G1 ballistic coefficient and a 100-yard zero.

Range	Velocity	Energy	Elevation	Time of Flight
Muzzle	1,010 fps	1,473 ft-lbs	—	0.00 sec
100 yd	964 fps	1,342 ft-lbs	0.00″	0.30 sec
200 yd	925 fps	1,235 ft-lbs	-35.86″	0.62 sec
300 yd	891 fps	1,146 ft-lbs	-112.19″	0.95 sec

Trajectory note: The elevation figures represent a ballistic trajectory calculated around a 100-yard zero. The 0.00-inch value at 100 yards represents the zero and should not be interpreted as indicating that gravity produces no projectile drop between the muzzle and 100 yards.

Why SOCOM XL Matters With a 650gr Projectile

The physical dimensions of the Maker REX illustrate why extended cartridge overall length matters. The projectile itself measures 2.035 inches long. Loading an exceptionally long projectile while remaining within the conventional AR-15 magazine envelope would require substantially more of that projectile to occupy space inside the cartridge case.

This 458 SOCOM Subsonic Ammo is loaded to 2.802 inches OAL, allowing the long Maker REX projectile to be seated farther out and preserving additional usable case capacity.

The chamber doesn’t get longer. The cartridge gets more room.

That distinction is fundamental to Chattahoochee Munitions’ SOCOM XL configuration. The chamber and cartridge case remain .458 SOCOM; the compatible firearm and magazine system provide additional usable cartridge overall length.

For more information about CM firearms, ammunition and components built around this concept, visit Terminal 458.

Factory-New Starline 458 SOCOM Brass

Each round of 458 SOCOM Subsonic Ammo is assembled using factory-new Starline .458 SOCOM brass rather than previously fired cases.

Combined with the CNC-machined Maker projectile, new Starline brass provides a quality foundation for ammunition developed specifically around CM’s heavy-projectile SOCOM XL application.

IMPORTANT — BOLT-ACTION USE ONLY

This 458 SOCOM Subsonic Ammo loaded with the 650gr Maker REX is intended for compatible bolt-action firearms only.

It is not intended for conventional AR-15 firearms, mini actions or the CM10 semi-automatic platform.

This does not mean SOCOM XL capability is inherently limited to bolt-action firearms. Chattahoochee Munitions also implements SOCOM XL extended-OAL capability in the CM10 large-frame semi-automatic platform. However, semi-automatic operation requires ammunition developed around the gas and cycling requirements of that platform.

CM10 owners should use the separately developed 458 SOCOM Semi Auto Ammo. That 650gr Maker REX load is configured at a 2.790-inch OAL with a propellant configuration selected specifically for CM10 semi-automatic operation.

458 SOCOM XL Firearm and Magazine Requirements

This 458 SOCOM Subsonic Ammo requires a firearm specifically capable of accepting its 2.802-inch cartridge overall length. Chattahoochee Munitions offers compatible CM7S .458 SOCOM bolt-action firearms configured for SOCOM XL extended-OAL capability.

Because this ammunition is loaded beyond conventional AR-15 magazine length, it also requires an appropriate feeding system. Complete compatible CM7S firearms use the Chattahoochee Munitions 458 SOCOM XL Magazine, a purpose-modified MDT metal AICS-pattern magazine that provides the additional usable cartridge length required by the 2.802-inch load.

Firearm Requirements

• Compatible .458 SOCOM chamber
• Bolt-action platform capable of accepting SOCOM XL extended-OAL ammunition
• Magazine and feeding system capable of accepting 2.802″ OAL ammunition
• 1:10 barrel twist or faster

Do not attempt to use this ammunition in a conventional AR-15 magazine or firearm that cannot safely accommodate its cartridge overall length.

Learn More About 458 SOCOM Subsonic Performance

Heavy projectiles, fast barrel twist and extended cartridge overall length are central to this application. For a deeper explanation of how these factors interact, read the Chattahoochee Munitions guide to 458 SOCOM Subsonic performance.

You can also explore Terminal 458 for Chattahoochee Munitions .458 SOCOM firearms, SOCOM XL configurations, ammunition, magazines and related products.

Frequently Asked Questions

Is this 458 SOCOM Subsonic Ammo compatible with an AR-15?

No. This ammunition is loaded to an extended 2.802-inch overall length and is not intended for conventional AR-15 firearms or AR-15 magazines.

Does 458 SOCOM XL use a different chamber?

No. The chamber remains .458 SOCOM. SOCOM XL refers to the additional usable cartridge overall length provided by a compatible firearm and magazine configuration.

How fast is the 650gr Maker REX load?

Chattahoochee Munitions recorded an average velocity of 1,010 fps over a 10-shot chronograph sample from a 12.5-inch barrel.

What barrel twist is required?

The 650gr Maker REX has a recommended 1:10 twist rate. This ammunition should be used only in a firearm with the appropriate barrel twist and cartridge-length compatibility.

Is this ammunition compatible with the CM10?

No. This specific 458 SOCOM Subsonic Ammo is for compatible bolt-action firearms only. The CM10 supports SOCOM XL extended-OAL capability, but semi-automatic operation requires a separately developed ammunition configuration. CM10 owners should use the 458 SOCOM Semi Auto Ammo developed specifically for that platform.

What magazine is required?

The ammunition requires a magazine and firearm capable of accepting its 2.802-inch OAL. Compatible complete CM7S firearms use CM’s purpose-modified 458 SOCOM XL Magazine.

What brass does Chattahoochee Munitions use?

This ammunition is loaded using factory-new Starline .458 SOCOM brass.

Is the 650gr Maker REX lead free?

Yes. The Maker REX is a CNC-machined solid-copper projectile and contains no lead.

How long is the 650gr Maker REX projectile?

The projectile itself measures 2.035 inches long. The completed CM cartridge is loaded to an overall length of 2.802 inches.