Spatha-15 Duty and Competition Upper

Our uppers are assembled by SOTAR-trained master armorers in North Carolina using components manufactured exclusively in the USA.

Below are some highlights of features of our Spatha-15DC upper:

• Barrel: Criterion 16″ Hybrid Profile, Mid-Length, Dimpled, .223 Wylde, 4150 CroMoV, Chrome Lined, Manganese Phosphate Barrel
  • 16″ makes it easy to stay legal with a carbine.  A mid-length gas system is ideal for a 16″ barrel.  We use a dimpled barrel for added assurance and alignment of the gas block.  We use a .223 Wylde chamber because it is the best blend of the reliability of the 5.56 NATO chamber headspace and the accuracy of the .223 Remington chamber geometry.  We use 4150 Chrome Molybdenum Vanadium steel over stainless for durability.
  • For our DC level finish, we upgrade to a chrome lined barrel.  Hard chrome lining is the Mil-Spec because it can withstand prolonged high rates of fire without eroding the throat and bore.  A chrome
  •  lined barrel will last significantly longer than one that is not chrome lined (2-4 times longer).  Criterion knows how to chrome line a barrel.  One of the legacy problems with chrome lining is that it degrades accuracy.  Not with Criterion barrels.  They have mastered the application of hard chrome to the bore of a barrel.  The bores are honed and hand lapped for the ultimate smoothness.
• Bolt Carrier Group: Para Bellum Arms Enhanced DLC BCG
  • We are very proud of all of our BCGs.  We worked with Microbest, Sprinco, and Michiguns to design the best product from the ground up.  For our DLC BCG, we started with our amazing phosphate BCG and upgraded the finish of the bolt head, carrier, gas key, and cam pin to Diamond Like Carbon (DLC).  Put simply, DLC is the slickest and hardest finish you can put on a bolt carrier group.
  • Our BCGs all feature the following upgrades over Mil-Spec:
    • Michiguns Optimized Carrier Key Screws (O.C.K.S.)
    • Sprinco Extra Power 5-coil extractor spring (we also include a standard power extractor spring)
    • Sprinco extractor O-ring (we also include a standard extractor insert)
    • Sprinco ejector spring
    • Sprinco gas rings
    • Ind
      ex-marked cam pin
  • For more information about our BCGs, check out the dedicated product page.
• Charging Handle: Radian Raptor Ambidextrous Charging Handle
  • Few people will scoff at the Raptor.  Radian makes the best ambidextrous charging handle on the market.
• Forward Assist: Forward Controls Design Low Drag Forward Assist (LDFA)
  • The forward assist can get caught on gear.  That is one of the reasons some upper designs have eliminated the forward assist altogether.  But then you lose the function of the forward assist: instead of being able to bump an unseated bolt into battery, you have to rack the charging handle again (and potentially again and again until the round seats); instead of being able to quietly cycle the bolt manually, you have to rack it hard to let momentum put the bolt into battery.  So, we will not build an upper without a forward assist.  The LDFA from Forward Controls Design eliminates the flange on the end of the forward assist button, which reduces the likelihood that it will get caught on gear.
• Gas Block: Superlative Arms DI Adjustable Gas Block (Set Screw)
  • Superlative Arms’ bleed off adjustable gas blocks are second to none.  With the option to control the volume of gas entering the gas system by both restriction and bleed off mechanisms, taming the gas flow for any length gas system, suppresses or unsuppressed, becomes a simple exercise.  The design prevents fouling of the detent mechanism, so you will always be able to adjust it and it will never adjust itself away from your desired setting.
  • Low profile gas blocks fit under handguards for a clean look, maximal rail real estate, and protection against burns. Set screw gas blocks are much more secure than clamp on gas blocks, but not as difficult to change as pinned gas blocks.
• Gas Tube: Melonite Mid-Length Gas Tube
  • We use gas tubes with a black melonite finish because the standard gas tube finish is stainless (and we don’t like the flash of silver under the handguard) and it won’t burn off.
• Muzzle Device: Precision Armament HYPERTAP Muzzle Device
  • The HYPERTAP is the most effective tunable muzzle device on the market.  It is both a muzzle brake and a compensator, so it reduces recoil and leverages the flow of gas to control muzzle rise.  Both of these effects mean visualizing hits on target and quick follow up shots.

Critical finishes and dimensions of individual components are inspected before we accept them into inventory.  To learn more about our quality control gauging and inspection, visit our Quality Promise page.

Each upper receiver includes the following assembly and QC steps (full schedule of all 82 points of inspection for our builds can be found in our Quality Promise page):

• Chamber headspace verified with your bolt.
• Barrel feed ramps expertly re-profiled (Colt modification, shingling corrected, encroachment corrected) and polished to a mirror finish.
• Barrel dimpled for gas block set screw.
• Barrel extension and barrel nut threads lubricated with AeroShell 64 grease.
• Barrel nut exercised and torqued to 55 ft. lbs. (M4E1 Enhanced Upper).
• Barrel muzzle threads coated with Molykote G anti-seize (for muzzle devices that use a crush washer or lock nut).
• Flash hider properly timed and lock nut torqued to 20 ft. lbs. per manufacturer specifications.
• Gas block/gas port alignment visually verified with borescope and gas system illuminator.
• Rocksett thread locker applied to gas block set screws.
• Gas block set screws torqued to 20 in. lbs. (proper torque with Rocksett).
• Performed by Microbest:
  • Bolt carrier/gas key properly sealed with Permatex aviation gasket.
  • Gas key screws properly torqued to 50-58 ft. lbs. and staked in two locations per screw.
  • Every bolt is high pressure tested with a proof load (not pressurized air) and undergoes magnetic particle inspection.
• Cam pin index-marked.
• Full lubrication with our own lubricant blend per our standard procedure.
• Full safety and function check per our standard procedure.
• Live fire test with a minimum of 3 rounds of M193 (troubleshoot and correct root cause of any malfunction).

The tables below detail what we put in the upper and what you are paying.

Spatha-15DC Upper Receiver (Black)

Spatha-15DC Upper Receiver (FDE)

For detailed material specifications for the components, see our Build Kit Spec Sheet.