500 PHANTOM Advanced Weapons System (AWS)
The Ghost from the Machine....


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I'll keep this simple - have you ever felt like Tim Allen, and just needed more power?? If you have, then let me introduce you to the 500 PHANTOM.....

As with the “smaller” .458 SOCOM AWS, the .500 Phantom AWS was designed to meet specific criteria when deployed from a specific weapons platform. Whereas the .458 SOCOM was designed for use in the AR-15 platform, the .500 Phantom is intended for the larger AR-10 platform. Basic criteria were the use of unmodified magazines and lower receivers, minor modifications to the upper receiver and bolt group, and minimal changes to outward appearance. In addition, the largest feasible case that would function reliably, as well as the use of .510 caliber projectiles and sabots.

The initial design, dubbed the .510 Phalanx, used a 2.00” long case with the largest available case diameter outside of the .50 BMG cartridge. A heavily rebated rim and prominent shoulder for headspace control were included in the design as well. Several prototype cases were formed, and ballistic simulations predicted acceptable performance. Unfortunately, however, quality of the brass for the prototypes left to be desired and the project was initially shelved. Pictured below are some of the initial .510 Phalanx prototypes.

The .510 Phalanx loaded with differnt projectiles is
shown next to the .308 Winchester (far left), the .303
British (center) and the .30-06 (far right)

The .510 Phalanx shown in the magazine for the No. Mk1
SMLE (far left) as well as the FN-FAL (left). On the right
cartridges originally intended for these magazines
(magazine for M1918 BAR in the .30-06 not shown)

Due to a lack of high quality brass, the Phalanx project sat on the back burner for a few monthes. The project was brought back to life with a new direction and a different case design was proposed. By going to a slightly smaller diameter case, a more prevalent parent case of improved quality could be used. Furthermore, the case length was reduced to 1.535” for two reasons: To be able to employ the .50-to-.30 caliber sabot and still meet desired overall loaded length of 2.75”, and the ability to employ the 750-grain Hornady A-Max bullet and meet desired overall loaded length of 3.34”. Two additional changes were incorporated, namely the use of the standard magnum rim size, and strengthening of the web to be able to operate the cartridge at higher pressures.

The final case design, dubbed the .500 Phantom, is shown in various loaded lengths below :

L to R: 308 Winchester, 500gr HawkRN, 700gr Hawk SP, 525g Barnes Solid RN,
570g Barnes XLC, 168g Sierra MK Sabot, 649g M8 API, 750g Hornady AMAX

The cartridge will function from standard AR-10 lowers and magazines, and the 20-round OEM magazine will accept at least 6 of the Phantom cartridges. The DPMS LR-308 rifle can also be modified to accept this cartridge. By using the standard magnum rim size, the OEM bolts designed for use with the WSM or RSAUM line of cartridges can be used without further modification. Existing upper assemblies can be converted to .500 Phantom by rebarreling and adjusting the gas system.

Armalite AR-10A4

Top, DPMS LR-300 mag with 700g Hawk
Bottom, AR-10 mag with 168g .308 in sabot

In addition to the gas operated AR-10 and LR-308, standard and short length bolt action rifles can be modified to accept this new cartridge. With the prevalence of the WSM and RSAUM line of cartridges, any bolt action rifle chambers in any of those cartridges can relatively easily be converted to the .500 Phantom AWS.

Remington 700 (switchbarrel) chambered in 500 Phantom AWS w/ Suppressor

Performance tests and initial prototyping were performed using an AR-10 with 24-inch Pac-Nor 1-in-9 twist barrel. The barrel was equipped with a JP Enterprises Recoil Eliminator muzzle brake, JP free floated hand guard, and SPR pistol grip. The test loads were developed using QuickLoad internal ballistics software, and maximum operating pressure set at 50,000 psi.

Initial test loads consisted of the 525gr Barnes Solid (2000fps), 570gr Barnes XLC Spitzer (1750fps) and the 750gr Hornady AMAX (1000fps). Load data is currently being developed and you can monitor the updates as they are posted on the Load Data Page - updated everytime I get to the range.

A loading block with rounds ready to be tested:

For anyone looking for the ultimate in gas operated shoulder fired power, the .500 Phantom should fit the bill. Formed and head stamped brass is available from Garber Supply Company and reloading dies are available from CH4D. All gun inquiries should be directed to Marty at Teppo Jutsu.

If you want to hear more of the history behind the 500 Phantom, check out this page that goes into more detail and the tale of building a new wildcat.



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