375 Subsonic Ammo – 400gr Maker REX – Semi-Auto
Chattahoochee Munitions 375 Subsonic Ammo combines the 400-grain Maker REX expanding projectile with a load configuration developed specifically for semi-automatic 375 Raptor firearms. Loaded to a 2.790-inch cartridge overall length, this ammunition is configured to support reliable magazine feeding while providing the operating characteristics required for semi-automatic use.
Chattahoochee Munitions recorded an average velocity of 1,012 fps during a 10-round chronograph sample fired through a 12.5-inch semi-automatic 375 Raptor firearm. This is measured CM test data rather than a calculated or single-shot velocity.
This semi-automatic load can also be used in compatible bolt-action 375 Raptor firearms. However, shooters whose primary objective is minimizing suppressed report from a bolt-action platform should select the dedicated Chattahoochee Munitions 400gr bolt-action subsonic load.
375 Subsonic Ammo Configured for Semi-Automatic Operation
This 375 Subsonic Ammo is a separately configured load developed around the operating requirements of semi-automatic 375 Raptor firearms. It is not simply the bolt-action version packaged for a different firearm type.
The semi-auto cartridge is loaded to a 2.790-inch COAL to support reliable feeding from compatible magazines. Chattahoochee Munitions also configures the ammunition specifically around semi-automatic operation while keeping the internal load specification proprietary.
The result is a 400-grain subsonic load intended for shooters who want the Maker REX projectile in a semi-automatic 375 Raptor platform without sacrificing the ability to use the ammunition in a compatible bolt-action firearm when needed.
400gr Maker REX Expanding Projectile
At the front of this 375 Subsonic Ammo is the Maker Bullets 400 Grain .375 REX projectile. Maker precision CNC machines the projectile from solid copper, resulting in a lead-free expanding projectile engineered specifically for subsonic applications.
According to Maker Bullets, REX projectiles are designed to expand to nearly three times their original diameter while maintaining nearly 100% of their original weight. Maker engineers individual REX projectiles to operate within specified velocity ranges across different calibers and firearm platforms.
Maker 400gr REX Projectile Specifications
- Projectile: Maker REX Subsonic Expanding
- Construction: Solid Copper, Lead Free
- Diameter: .375″
- Weight: 400 grains
- Projectile Length: 1.81″
- Sectional Density: 0.406
- Ballistic Coefficient: 0.49
- Maker Recommended Twist Rate: 1:11 or faster
1,012 FPS Average from a 12.5-Inch Semi-Auto
During Chattahoochee Munitions testing, this 375 Subsonic Ammo produced an average velocity of 1,012 fps from a 10-round chronograph sample fired through a 12.5-inch semi-automatic 375 Raptor firearm.
Actual velocity can vary between individual firearms and with barrel length, atmospheric conditions and other variables. The published 1,012 fps figure represents the average measured during the stated CM test rather than a guaranteed velocity from every firearm.
Semi-Auto and Bolt-Action Compatibility
Although this 375 Subsonic Ammo is specifically configured for semi-automatic operation, it can also be used in compatible bolt-action firearms properly chambered for 375 Raptor.
There is, however, an important distinction between compatibility and optimization. Chattahoochee Munitions offers a separate 400gr subsonic load specifically configured for bolt-action use. The different internal configuration required by the semi-automatic load produces a greater suppressed report when fired from a bolt-action platform than the dedicated bolt-action ammunition.
For a semi-automatic 375 Raptor firearm, select this version. For a suppressed bolt-action firearm where minimizing sound is the priority, the dedicated bolt-action 400gr load is the preferred option.
Converted Starline Brass
Chattahoochee Munitions manufactures this 375 Subsonic Ammo using cases converted from Starline .358 Winchester brass. The converted cases retain Starline’s original .358 WIN headstamp even though the completed ammunition is 375 Raptor.
The headstamp therefore identifies the parent brass rather than the chambering of the completed cartridge. Customers should identify this ammunition by its packaging and intended chambering rather than relying on the case headstamp.
IMPORTANT AMMUNITION WARNING: This ammunition is manufactured using brass converted from Starline .358 Winchester cases and therefore retains a .358 WIN headstamp. The completed ammunition is 375 Raptor ammunition. It must not be chambered or fired in a .358 Winchester firearm or any firearm not properly chambered for 375 Raptor.
375 Subsonic Ammo Specifications
- Caliber: 375 Raptor
- Projectile: Maker REX Subsonic Expanding
- Projectile Weight: 400 grains
- Projectile Diameter: .375″
- Projectile Construction: CNC-Machined Solid Copper, Lead Free
- Ballistic Coefficient: 0.49
- Sectional Density: 0.406
- Maker Recommended Twist Rate: 1:11 or faster
- Cartridge Overall Length: 2.790″
- Measured Average Velocity: 1,012 fps
- Velocity Test: 10-shot chronograph sample
- Test Barrel Length: 12.5″
- Test Platform: Semi-Automatic 375 Raptor
- Primary Application: Semi-Automatic
- Bolt-Action Compatible: Yes
- Brass: Converted Starline .358 Winchester
- Case Headstamp: .358 WIN
- Package Quantity: 20 rounds
Choosing the Correct 400gr 375 Raptor Load
Chattahoochee Munitions offers two versions of its 400gr Maker REX subsonic 375 Raptor ammunition because semi-automatic and bolt-action firearms have different operating requirements.
This 375 Subsonic Ammo is the correct choice for a semi-automatic 375 Raptor firearm. Its 2.790-inch COAL supports semi-automatic feeding, while its overall load configuration is developed specifically for semi-automatic operation.
The semi-auto ammunition remains compatible with properly chambered bolt-action firearms, making it the more flexible choice when ammunition may be used across both firearm types. The dedicated bolt-action load remains the preferred choice for shooters seeking the lowest suppressed report from a bolt-action platform.
Part of the Chattahoochee Munitions 375 Raptor System
This 375 Subsonic Ammo is developed to complement Chattahoochee Munitions semi-automatic 375 Raptor firearms and the broader CM 375 Raptor product family. Chattahoochee Munitions develops firearms, suppression systems and ammunition around the cartridge as components of a complete 375 Raptor platform.
For additional information about the cartridge, available firearms and related ammunition, visit the Raptor Paddock.
Frequently Asked Questions
What projectile is used in this 375 Subsonic Ammo?
This ammunition uses the Maker Bullets 400-grain .375-caliber REX solid copper expanding projectile. Maker lists the projectile at 1.81 inches long with a 0.406 sectional density and 0.49 ballistic coefficient.
What velocity does the semi-auto ammunition produce?
Chattahoochee Munitions recorded an average velocity of 1,012 fps from a 10-shot chronograph sample fired through a 12.5-inch semi-automatic 375 Raptor firearm. Actual velocity can vary between firearms and operating conditions.
What is the cartridge overall length?
The semi-automatic version is loaded to a 2.790-inch cartridge overall length to support reliable feeding in compatible semi-automatic platforms.
Can I use this ammunition in a bolt-action 375 Raptor?
Yes. This ammunition can also be used in compatible bolt-action firearms properly chambered for 375 Raptor. However, the dedicated Chattahoochee Munitions bolt-action 400gr load is preferable when minimizing suppressed report from a bolt-action platform is the priority.
Why are there separate semi-auto and bolt-action loads?
Semi-automatic and bolt-action firearms have different operating requirements. Chattahoochee Munitions configures each version for its intended platform rather than using one compromise load for both applications.
Why does the case say .358 WIN?
Chattahoochee Munitions converts Starline .358 Winchester brass for this ammunition. The original .358 WIN headstamp remains on the converted case even though the completed cartridge is 375 Raptor ammunition. It must never be fired in a .358 Winchester firearm.
How many rounds are included?
Each box contains 20 rounds of 400gr 375 Raptor subsonic ammunition.
What barrel twist does Maker recommend?
Maker Bullets recommends a barrel twist rate of 1:11 or faster for its 400gr .375 REX projectile.
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