Iron-Pig Armament


MSRP: $699.00
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96.00 Ounces

The STANDARD MilSpec Gladiator 556M Upper Receiver comes standard with the Iron Pig  Forged Gen II Upper, Billet M-lok handrail with an 16 inch, 1:8 twist barrel, and M16 BCG & MilSpec A2 Muzzle Device.

If you would like to customize your upper, click on COMPLETE GLADIATOR  UPPER RECEIVER-CUSTOM.


These barrels are properly air-gauge tested and individually checked for headspace. 0ur quality control system ensures they are dimensionally correct and bores fall well within their individual tolerance ensuring superior accuracy.

  • Length: 16″
  • Weight: 29.0 ounces
  • Caliber: 5.56 NATO
  • Gas System: Carbine Length
  • Twist Rate: 1:8 RH
  • Gas Block Journal: .750″
  • Gas Port Size: .063″
  • Muzzle Thread: 1/2-28
  • Material: 4140 CMV
  • Finish: Blacknitride+™ by H&M
  • Barrel Extension: M4
  • 11° Target Crown


  • Receivers are precision machined from high quality forgings and fit all standard Mil-Spec style AR15 lower receivers. They do not have dry film lube applied. 

    • 7075-T6 Aluminum Forging
    • Hard Coat Anodized
    • No T-Marks
    • 100% American Made


IPA AR-15 Lightweight M-LOK Handguard w/ Full Rail

  • Finish: Hard Anodized
  • Material: 6061-T6 Aircraft Grade Aluminum
  • Gun Rail: M-LOK
  • Steel Barrel Nut and Mounting Screws


M16 BCG which is trusted by seasoned shooters and depended on by experienced builders. Our goal is to go above and beyond Mil-Spec expectations! Iron Pig Armament’s BCGs are made to perform for tens of thousands of rounds. This is to ensure long-term reliability and the utmost durability and improved lubricity for our BEST-IN-CLASS BCG that is 100% American Made!


Bolt (May or may not have HPI MPI SP on bolt)

  • Machined from Carpenter Technology No. 158 alloy.
  • Heat treated
  • Shot peened per ASTM B851/SAE AMS2430S
  • Individually High Pressure Tested (test fired)
  • HP proof testing, 100% using a high pressure M197 or SAAMI commercial equivalent, without evidence of failure
  • Individually Magnetic Particle Inspected after Initial Test Fire
  • Manganese Phosphate Finish


  • 4140 Steel per ASTM A108, cold drawn and stress relieved BHN 187-22
  • Phosphate Finish
  • Extractor Spring
  • Black Extractor Insert
  • Viton O-Ring


  • Machined from AISI 8620 aircraft quality alloy per ASTM A108/A322-13
  • Full Mass M16 Profile
  • Stress Relieved
  • Hard Chrome Bore

Gas Key

  • Machined from 4130 chromoly steel alloy per ASTM A108/A322-13
  • Grade 8 Hardware
  • Properly Staked
  • Hard Chrome Internal
  • Permatex sealed