Spatha-15 Enhanced Mil-Spec 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-15EM upper:

• Barrel: PBA 16″ Government Profile, Mid-Length, Dimpled, 5.56 NATO, 4150 CroMoV, Nitride 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 5.56 NATO chamber because it is Mil-Spec and has a robust and reliable geometry.  We use 4150 Chrome Molybdenum Vanadium steel over stainless for durability.  We use a nitride finish, inside and out, because it is robust.
  • Note that our EM and FC carbine barrels are NOT chrome lined, per Mil-Spec.  This is because chrome lining has to be done really well for it to not have an adverse effect on accuracy, and barrels from manufacturers that do it well (i.e. Criterion) are very expensive for this finish level (generally, a good chrome-lined barrel will cost between $300 and $500).  Besides, the Mil-Spec calls for chrome lining to withstand the high heat from long strings of rapid fire, and this need isn’t as prominent for most civilians.  A non-chrome-lined barrel will wear faster than a chrome lined barrel, but the long term benefit does not warrant the upfront cost for most.  Note that our DC Spatha uppers feature chrome-lined Criterion barrels.
• Bolt Carrier Group: Para Bellum Arms Enhanced Phosphate 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 Phosphate BCG, we started with a “phosphate everything” approach (except the hard chrome lining of the gas key and carrier and the firing pin).  Manganese phosphate is the Mil-Spec for BCG finishes and offers good surface hardness and holds lubricant very well.
  • 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
    • Index-marked cam pin
  • For more information about our BCGs, check out the dedicated product page.
• Charging Handle: Mil-Spec Charging Handle
• Gas Block: Low Profile Gas Block (Set Screw)
  • 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: Mil-Spec A2 Flash Hider

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 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 torqued to 10-20 ft. lbs.
• 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-15EM Upper Receiver (Black)

Spatha-15EM Upper Receiver (FDE)

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