Zeus Arms PROTEUS 556/300BO

That’s right!! 556 and a 300 black out from the same gun. All you need to do is change the barrel!!

comes with both barrels, hard case and 6 magazines


This current model is special order only. 6-8 weeks lead time




Our PROTEUS Series is our most popular pistol offering. This firearm is meant to be the ultimate compact survival gun. The Proteus features a QD removable Barrel system and foldable brace assemble allowing you to transport in a backpack or pistol case. Due to the unique QD Barrel removal system you can also transition between compatible calibers in seconds.

Lower Receiver: The Proteus pistol is currently made on our GHOST lowers which we spend the extra time to engrave the serial number on the bottom side of the lower to leave a sleek clean blank finish on the sides to customize to your liking.

  • Enhanced Flared Magazine Well
  • Type III Hard Coat Anodized
  • 7075-T6 aluminum
  • Precision CNC Machine broached magazine well
  • Accepts all mil-spec components


Lower parts Kit: Our lower parts kits contain all high quality, 100% USA produced components, manufactured to our exacting standards. We don’t use foreign made parts, polymer parts, or MIM parts.


Buffer Tube Kit/Side Folding: AR15 / M16 Buffer Tube Kit – Standard Carbine with Side Folding Attachment

• Mil-Spec dimension 7075-T6 6 position buffer tube – hard coat anodized
• Carbine buffer
• Castle nut – phosphate coated
• Endplate – mil-spec phosphate coated
• Buffer spring – Coated Music Wire


Brace: SB Tactical SBA3 Brace (Black)

Lancer Magazine: Best of both worlds. A Polymer body that doesnt dent like metal and metal feed lips that can handle the wear and tear years down the road. L5 Advanced Warfighter 30 Rounds- Black
• Hardened Steel Feed Lips
• Non-Tilt Follower
• Stainless Steel Spring
• Aggressive Texturing

Upper Receiver:
• 7075-T6 aluminum
• Machined from quality forgings
• No T-Marks
• Hard coat anodized
• Fits any mil-spec style AR15 / M16 lower receiver


Cry Havoc Barrel QD Attachment allowes for barrel assembilies to be quickly removed for compact storage and to allow for quick barrel swaps between compatible calibers


Barrel: Our barrels are produced from raw bar stock to finished product at a single state of the art facility. We drill, ream, rifle, contour, and assemble, using the lastest in robot automation technolgy. All of our barrels are properly stress relieved after rifling, and extensions are torqued after nitride.  Our quality control system ensures that all barrels are dimensionally correct and bores fall well within their individual tolerance.

  • 7.5″ length
  • 5.56 NATO Chamber
  • Pistol gas system
  • .750″ gas block journal
  • 1:7 RH twist
  • 4150 CMV
  • Stress relieved after rifling
  • Black Nitride finish
  • M4 extension
  • 100% USA Made


Muzzle Device: Equipped with flash can which is perfect for those applications that do not need recoil or flash reduction, but still need to focus muzzle blast and flash down range. Our flash cans are slim enough to fit under most handguards for that classic “SD” look. Because there is no direct impact on the muzzle device, the lightweight aluminum is not damaged during firing.

  • Machined from 6061-T6 aluminum
  • Hard coat anodized
  • Threaded 1/2-28
  • Outside diameter: 1.20″
  • Length: 1.75″
  • Weight: 1.7 ounces
  • 100% American Made

• Machined from 6061-T6 aluminum
• Hard coat anodized per milspec
• 6061-T6 lightweight barrel nut
• Top rail length: 7 inches
• MLOK mounting points at 3:00, 6:00, and 9:00


Gas System: Our Gas Block and our gas tube get nitride coated for better resistance against carbon build up than your standard stainless gas tubes.

  • Machined from 4140 pre-hardened steel
  • Black Nitride coated
  • Closed end gas tube hole
  • 100% USA Made


Ambi Charging Handle:
• Body Manufactured to milspec dimensions
• Fits all standard AR15 / M16 style firearms
• Machined from a 7075-T6 forging for extra strength
• Hard coat anodized – black

Bolt Carrier Group:

  • 8620 M16 style carrier
    • Black Nitride finish
    • Properly heat treated
    • Final grind before plating
  • Carpenter 158 5.56/.223 bolt
    • Heat treated
    • Shot peened
    • Precision ground for perfect dimensions
    • Black Nitride finish
    • MPI
  • 4140 billet gas key
    • Black Nitride Finish
    • Properly seated with Grade 8 fasteners
    • Properly staked to ensure reliability
  • 4140 Cam Pin nitride treated for wear resistance
  • Billet Machined Extractor
    • Machined from solid 4140 bar stock, heat treated and shot peened
    • Phosphate coated for reliable extraction
    • Extractor insert included
    • O-Ring included
  • Firing pin precision machined from 17-4 H-900 Stainless Steel
  • 100% USA Made

All Zeus Firearms ship with a hard case for easy transportation


There are no reviews yet.

Only logged in customers who have purchased this product may leave a review.