QUALITY CARTRIDGE CAN SUPPLY BRASS FOR THE .500 PHANTOM AND THE REAMER AND HEAD SPACE GAGES MAY BE OBTAINED FROM MANSON PRECISION REAMERS.

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 were requirements set forth by the project sponsor.


(L to R) .308 168 gr in sabot, 500 gr. Hawk, 570 gr. Barnes XLC,
700 gr Hawk, 650 gr. GI M2 Ball, seated, 308 Winchester 

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 shows the 500 Phantom being formed.


(L to R) 500 Jeffery, Shortened, Formed, Trimmed,
Seated 700g Hawk Spz, 308 Winchester 

With the arrival of a new project sponsor, the idea was brought back to life, 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.

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

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.

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.

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 starting loads were developed using QuickLoad internal ballistics software, and maximum operating pressure set at 50,000 psi.

While load development continues, initial results show all criteria were met if not exceeded.  A sampling of the results is given below.  (Velocities were collected using a F-1 Chrony, and groups were measured at 100 yards. )

PROJECTILE

VELOCITY

ENERGY

GROUP

Barnes 300 gr FN   2590 fps 4468 ft-lbs N/A
HAWK 500 gr Spitzer   1810 fps 3637 ft-lbs 1.00"
Barnes 570 gr XLC   1688 fps 3606 ft-lbs 1.03"
M8 649 gr API   1119 fps 1804 ft-lbs N/A
Hornady 750 gr AMAX   1123 fps 2100 ft-lbs 1.136"

For anyone looking for the ultimate in gas operated shoulder fired power, the .500 Phantom should fit the bill. Formed and headstamped brass is available from Garber Supply Company, reloading dies are available from CH 4 D, and bolt action rifles in this caliber can be ordered through Sportsmans Guns.

ONE OF FOUR CUSTOM BUILT AR-15 (!!!) UPPERS IN .500 PHANTOM, USING OLYMPIC ARMS WSSM COMPONENTS AND OUR CUSTOM MUZZLE BRAKE.

THE FEISTY ROOSTER's GUN PAGES 
I enjoy shooting. I really enjoy shooting something unique. While I appreciate the
simple, unspoiled pleasure in shooting a .243, a 30-30 or a 30-06, my secret joy
comes from atypical cartridges. I've begun to list some of them below. Hopefully
this list will grow to include a magical collection of the useful, unusual and the exotic.

Be sure to visit the second home of the 500 Phantom

 

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Last modified: June 1, 2011