Technical Reference
AR-15 Mil-Spec Standards: Complete Reference
Specifications for every major AR-15 component, pulled from published military technical data packages, SAAMI standards, and manufacturer material sheets. If a number is on this site, its source is cited beside it.
What "Mil-Spec" Actually Means
Mil-spec is shorthand for conformance to the military Technical Data Package (TDP) for the M16 and M4 family of rifles. The TDP is a bundle of drawings, material callouts, process specs, and inspection criteria maintained by the US Army. It does not describe a single rifle. It describes the minimum acceptance criteria a part must meet to be supplied to the military for service use.
Commercial AR-15 parts range from exceeding the TDP (target match barrels, tighter tolerance billet receivers) to failing it outright (cast receivers, untested bolts, understaked gas keys). "Mil-spec" alone is neither a floor nor a ceiling on quality. It is a specific document set, and a part either meets the callouts or it does not.
Key mil-spec documents referenced throughout this guide:
- MIL-B-11595E: Steel, Chrome-Molybdenum-Vanadium for Gun Barrels
- MIL-A-8625 Type III: Anodic Coatings for Aluminum, hard anodize class
- MIL-DTL-16232: Phosphate Coatings, Heavy, Manganese or Zinc Base
- MIL-STD-1916: DoD Preferred Methods for Acceptance of Product
- TDP drawings: M16A2 / M4 Carbine Technical Data Package (dimensional callouts for bolt, carrier, barrel extension, receivers)
Spec Categories
Barrels
4150 CMV vs 4140 vs 416R stainless, MIL-B-11595E chrome lining, twist rate by bullet weight, 5.56 NATO vs .223 Wylde chambers.
View specificationsBuffer Systems
Carbine, H, H2, H3, and rifle buffer weights. Mil-spec (1.148 in) vs commercial (1.168 in) tube dimensions. Interactive weight calculator.
View specificationsQuick Reference Table
Common parts, the spec that matters, and the mil-spec value.
| Part | Spec | Mil-spec value | Why it matters |
|---|---|---|---|
| Lower receiver | Aluminum grade | 7075-T6 forged | Highest strength-to-weight of common aluminum alloys. |
| Lower receiver | Anodize | MIL-A-8625 Type III Class 2 | Hard coat anodize, 50 to 75 Rockwell C, corrosion and wear resistant. |
| Barrel | Steel | MIL-B-11595E (4150 CMV) | Chrome-moly-vanadium handles sustained fire better than 4140. |
| Barrel | Chamber | 5.56x45mm NATO | Longer leade handles both 5.56 NATO and .223 Rem safely. |
| Barrel | Chrome lining | 0.002 in min bore and chamber | Per MIL-B-11595E, extends service life and eases cleaning. |
| Bolt | Steel | Carpenter 158 | Called out by the military TDP for toughness and fatigue life. |
| Bolt | Testing | MPI and HPT | High pressure proof then magnetic particle inspection for cracks. |
| Carrier | Gas key | Grade 8 screws, properly staked | Staking prevents screws backing out under cyclic load. |
| Buffer tube | OD | 1.148 in (mil-spec) | Commercial 1.168 in stocks will not fit mil-spec tubes. |
| Trigger pins | Diameter | 0.154 in | Mil-spec lowers use small pin; large-pin Colt lowers use 0.170 in. |
Disclaimer: Specifications are sourced from published military technical data packages, SAAMI standards, and manufacturer data sheets. Always verify critical dimensions with calibrated measuring tools. This reference is educational and not a substitute for a qualified gunsmith.
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