M4E1 Threaded ATLAS S-ONE 5.56 Complete Uppers - Selectable Barrel and Handguard options and Finish

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Upgrade your AR15 with one of the full featured M4E1 Threaded ATLAS S-ONE  5.56 Complete Uppers.  Select barrel length, gas system, barrel profile, muzzle device, handguard length, and finish.

Ready: Pick Your Starting Point.

The first thing on your gear list is the gear focus. From shotgun cleaning kits to a Shockwave home defense pack, or even a steel target system, we've created the perfect starting points to accommodate a variety of situations, needs and adventures - and the list keeps on growing.

Set: Add Items To Your Bundle.

Next, is to assemble your bundle by scanning the different gear options. If it's a cleaning kit you're building, you may see a variety of options for brush calibers, solvents, and even cleaning pads. The gear options are shown in tiles and you simply need to click “Add to Bundle” for the items you need. Additional gear information will appear if you click the 'i' in the top left of the gear tile. Keep in mind, the more gear you select, the more you save. And as you grow the number of items in your bundle your discount will be shown in the top right of the screen. Here's how discounting works:

  • $25-$50 combined orders receive 5% off and free shipping!
  • Combined orders over $50 receive 15% off and free shipping!

Bundle!: Add To Cart & Purchase.

Once you add the first item to your bundle, a status bar will appear at the top showing the number of items in your bundle, a button to view your bundle summary, and sum of your building discount. At the bottom of the screen, you'll see the bundle price and simply click "Add to Cart" once your bundle is built.

And of course, if you need additional help with buidling your own custom bundle, don't hesitate to contact us.

Product Description

M4E1 Threaded ATLAS S-ONE 5.56 Complete Uppers include the new ATLAS S-ONE Handguard! The S-ONE line of handguards are designed with size and weight in mind, providing the perfect addition to your lightweight build. The proprietary ATLAS attachment system is a durable and dependable mounting platform, maintaining a slim profile while still providing the strength and stability customers have grown to love from Aero Precision handguards.

All complete uppers include:

  • M4E1 Threaded Upper Receiver
  • ATLAS S-ONE Handguard - some configurations have length options
  • CMV Barrel - choice of length and gas system
  • Barrel option - pinned and welded VG6 Epsilon 556SL option available with 14.5" Black Carbine and Mid-length configurations
  • Low profile gas block and gas tube to suit barrel
  • This complete upper does not include a BCG or Charging Handle

M4E1 Threaded Upper Receiver Features:

  • New enhanced forging that gives the upper receiver a "billet look"
  • New picatinny profile that blends seamlessly with the Enhanced Series Handguards
  • M4 Feedramps
  • .250 takedown pin holes
  • Laser engraved T-marks
  • Includes port door and forward assist installed

ATLAS S-ONE Handguard Features:

  • Front and rear picatinny rail
  • Eliminated center of top rail for weight reduction
  • Indexing grooves in 12:00 position for positive grip control
  • Quick disconnect sling socket at the 3, 6 and 9 o'clock positions
  • Compatible with low profile gas blocks
  • 1.3" Inside diameter
  • 1.5" Outside diameter
  • Compatible with mil-spec AR15 upper receivers and barrels

5.56 Barrel Features:

  • Chamber: 5.56
  • Twist: 1 in 7
  • Threading: 1/2"x28
  • Material: 4150 Chrome Moly Vanadium
  • Finish: QPQ corrosion resistant finish
  • Gas Block: .750 (note exceptions below)
  • Gas System:  some barrel lengths have choice of gas system
  • M4 Barrel Extension
  • HP and MPI Tested


  • 14.7" barrels can be pinned and welded with a standard A2 flash hider to yield an overall length of 16+"
  • 14.7" Pencil profile barrels require a .625 diameter gas block
  • 14.5" barrels with a pinned and welded VG6 Epsilon 556SL yield a 16+" overall length
  • The VG6 Epsilon 556SL has a .745" outside diameter, permitting full maintenance and removal of your gas block without having to remove the muzzle device

Aero Precision USA
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2.5 lbs
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