Description

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

The Spatha-15DDSR retains the following features of the FC model:

• Para Bellum Arms Precision Upper Receiver
  • The Para Bellum Arms Precision Upper is forged from 7075-T6 aluminum and precision machined to extremely tight tolerances. Note that the barrel socket is intentionally undersized for a tight fit — if you decide to change the barrel, you may need to heat the barrel socket with a heat gun or hairdryer first.
• 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 Tube: Melonite Mid-Length Gas Tube

The DDSR model includes the following upgrades to the FC model:

• Handguard: Geissele Super Modular Rail MK16, 13.5″
  • Standard issue on current SOCOM carbines (URG-I), this handguard is the ultimate battle rail.
  • Machined from 7075-T6 aluminum, this rail offers better strength and stiffness than most others.
  • The 7-sided M-LOK interface offers maximum real estate and versatility for accessories.
  • The steel-reinforced QD swivels offer low profile and long lasting sling attachment.
  • The low profile allows comfortable grip while using tactical lasers and lights.
• 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
    • Dimpled for added assurance and alignment of the gas block
    • .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
    • Chrome Molybdenum Vanadium (CrMoV) steel for durability.
    • Chrome lined barrel because it can withstand prolonged high rates of fire without eroding the throat and bore.
      • 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 and the result is match grade accuracy with the durability of hard chrome. The bores are honed and hand lapped for the ultimate smoothness.
    • HEADSPACE DISCLAIMER: Criterion barrels are manufactured to extremely tight tolerances.  In line with good quality control practices, a GO/min headspace gauge (minimum spec) will have a positive bias, meaning that the error is on the positive side of the target, to ensure only good product will pass (at the expense of rejecting good product that is close to the lower limit).  Because Criterion manufacturers to extremely tight tolerances and GO/min headspace gauges are likely oversized, their barrels may appear to fail headspace.  We have spoken with Criterion and Forster at great lengths about this, and we are confident in the barrels provided by Criterion.  If a Criterion chamber does not pass the 1.4646″ headspace gauge, we ensure that the bolt freely rotates using a 1.4636″ gauge.  For more information, please check out our Headspace Disclaimer article.
• Bolt Carrier Group: Para Bellum Arms Enhanced DLC BCG
  • Upgraded diamond-like carbon (DLC) on carrier, bolt head, and cam pin; phosphate everything else
  • Microbest sub-components (8620 carrier, C158 HPT/MPI bolt, 4340 cam pin, etc.)
  • 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
  • Index-marked cam pin
  • Coiled ejector roll pin
  • For more information about our BCGs, check out the dedicated product page.
• 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.
• Muzzle Device: Choice of Suppressor Host
  • We recognize and appreciate that every shooter has a preferred brand of suppressor. We offer several options for suppressor hosts, including bare muzzle threads for a direct thread can (note that we require shipment with thread protector).
• Charging Handle: Radian Raptor-SD Ambidextrous Charging Handle
  • We move to a Raptor-SD, which features a prominent gas blocking ridge and aggressive porting along the stem to minimize gas in the shooter’s face.

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 inspection points for our builds can be found in our Quality Promise page):

• Chamber headspace verified with your bolt (see our Headspace Disclaimer article).
• 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 50 ft-lb (Geissele)
• Barrel muzzle threads coated with Molykote G anti-seize (for muzzle devices that use a crush washer or lock nut) or Rocksett thread locker (for devices that use shims).
• Muzzle device properly timed torqued to 20 ft-lb or 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-lb (proper torque with Rocksett).
• VibraTite VC3 applied to handguard screws and screws torqued to 6-8 ft-lb (Geissele).
• Performed by Microbest:
  • Bolt carrier/gas key properly sealed with Permatex aviation gasket.
  • Gas key screws properly torqued to 50-58 ft-lb 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-15DDSR Upper Receiver (Black)