MIL-DTL-38999 & MIL-DTL-27599 Specification Standards Reference Guide
Comprehensive Military Standard Mapping for Circular Electrical Connectors (Series I, II, III, IV)
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This technical reference document provides a complete catalog of official Department of Defense (DoD) military standard specification sheets for circular, miniature, high-density, environment-resistant electrical connectors. Governed by MIL-DTL-38999 (crimp contact types) and MIL-DTL-27599 (solder contact types), these connectors are divided into four distinct series based on coupling mechanism, shell geometry, contact protection, and environmental resistance capabilities.
MIL-DTL-38999 & MIL-DTL-27599 Series I
Series Characteristics & Key Features: Series I connectors feature a 3-pin bayonet coupling mechanism requiring a quick quarter-turn to mate. They utilize a long shell design providing 100% scoop-proof protection, preventing any possibility of pin contact bending or accidental electrical shorting during blind mating at severe angles. Operating temperature ranges from -65°C to +175°C (or +200°C depending on class). Uses MS27xxx designations for crimp contacts and MS20xxx for solder contacts under MIL-DTL-27599.
| Specification Standard | Connector Style & Description |
| MS27466 | Wall Mounting Receptacle (Crimp Type, Bayonet Coupling, Front Panel Mount) |
| MS27656 | Wall Mounting Receptacle (Back Panel Mounting, Crimp Type, Bayonet Coupling) |
| MS27496 | Box Mounting Receptacle (Crimp Type, Bayonet Coupling, Front Panel Mount) |
| MS27505 | Box Mounting Receptacle (Back Panel Mounting, Crimp Type, Bayonet Coupling) |
| MS27467 | Straight Plug (Crimp Type, Bayonet Coupling, Grounding Fingers) |
| MS27468 | Jam-Nut Mounting Receptacle (Crimp Type, Bayonet Coupling) |
| MS27661 | Lanyard Release Plug (Fail-Safe Breakaway Coupling, Crimp Contacts) |
| MS27469 | Hermetic Wall Mounting Receptacle (Solder Contacts, Hermetic Seal) |
| MS27470 | Hermetic Jam-Nut Mounting Receptacle (Solder Contacts, Hermetic Seal) |
| MS27471 | Hermetic Solder Mounting Receptacle (Solder Contacts, Hermetic Seal) |
| MS20026 | Solder Wall Mounting Receptacle (Solder Type, Class T, MIL-DTL-27599 Series I) |
| MS20027 | Line / Cable Connecting Receptacle (Solder Type, Class T, MIL-DTL-27599 Series I) |
| MS20028 | Solder Straight Plug (Solder Type, Class T, MIL-DTL-27599 Series I) |
| MS20029 | Solder Jam-Nut Mounting Receptacle (Solder Type, Class P, MIL-DTL-27599 Series I) |
MIL-DTL-38999 & MIL-DTL-27599 Series II
Series Characteristics & Key Features: Series II connectors are engineered specifically for low Profile, lightweight, and space-critical applications. Unlike Series I, Series II connectors are non-scoop-proof, allowing for a significantly shorter shell length and up to a 20% weight reduction. They feature bayonet coupling and operate in temperature ranges up to +200°C. Includes MS27xxx crimp models, MS2733x solder models (MIL-DTL-27599), and D38999/10 dummy stowage receptacles.
| Specification Standard | Connector Style & Description |
| MS27472 | Wall Mounting Receptacle (Crimp Type, Bayonet Coupling, Front Panel Mount) |
| MS27497 | Wall Mounting Receptacle (Back Panel Mounting, Crimp Type, Bayonet Coupling) |
| MS27499 | Box Mounting Receptacle (Crimp Type, Bayonet Coupling, Front Panel Mount) |
| MS27513 | Box Mounting Receptacle (Extended Grommet, Crimp Type, Bayonet Coupling) |
| MS27508 | Box Mounting Receptacle (Back Panel Mounting, Crimp Type, Bayonet Coupling) |
| MS27474 | Jam-Nut Mounting Receptacle (Crimp Type, Bayonet Coupling) |
| MS27473 | Straight Plug (Crimp Type, Bayonet Coupling) |
| MS27484 | Straight Plug with Grounding Fingers (EMI Shielding, Crimp Type, Bayonet Coupling) |
| MS27500 | 90-Degree Elbow Plug (Crimp Type, Bayonet Coupling) |
| MS27475 | Hermetic Wall Mounting Receptacle (Solder Contacts, Hermetic Seal) |
| MS27476 | Hermetic Box Mounting Receptacle (Solder Contacts, Hermetic Seal) |
| MS27477 | Hermetic Jam-Nut Mounting Receptacle (Solder Contacts, Hermetic Seal) |
| MS27478 | Hermetic Solder Mounting Receptacle (Solder Contacts, Hermetic Seal) |
| MS27334 | Solder Wall Mounting Receptacle (Solder Type, Classes P and T, MIL-DTL-27599 Series II) |
| MS27335 | Solder Box Mounting Receptacle (Solder Type, Class T, MIL-DTL-27599 Series II) |
| MS27336 | Solder Straight Plug (Solder Type, Classes P and T, MIL-DTL-27599 Series II) |
| MS27337 | Solder Jam-Nut Mounting Receptacle (Solder Type, Classes P and T, MIL-DTL-27599 Series II) |
| D38999/10 | Dummy Stowage Receptacle (Bayonet Coupling, Series II) |
MIL-DTL-38999 Series III
Series Characteristics & Key Features: Series III connectors utilize a heavy-duty, self-locking triple-start stub thread coupling mechanism. They are 100% scoop-proof and designed for extreme environmental durability, supporting severe vibration (up to 44g random), high operating temperatures (up to +200°C), firewall capabilities, and high-level EMI/RFI shielding. Standardized under metric D38999/20 through D38999/36 and D38999/60-62 specification sheets.
| Specification Standard | Connector Style & Description |
| D38999/20 | Wall Mounting Flange Receptacle (Threaded, Removable Crimp Contacts) |
| D38999/21 | Box Mounting Flange Receptacle (Hermetic, Threaded, Hermetic Solder Contacts) |
| D38999/22 | Dummy Stowage Receptacle (Threaded, Series III) |
| D38999/23 | Jam-Nut Mounting Receptacle (Hermetic, Threaded, Hermetic Solder Contacts) |
| D38999/24 | Jam-Nut Mounting Receptacle (Threaded, Removable Crimp Contacts) |
| D38999/25 | Solder Mounting Receptacle (Hermetic, Threaded, Hermetic Solder Contacts) |
| D38999/26 | Straight Plug (Threaded, Removable Crimp Contacts) |
| D38999/27 | Weld Mounting Receptacle (Hermetic, Threaded, Hermetic Solder Contacts) |
| D38999/28 | Hexagon Nut, Connector Mounting (Series III & IV Metric) |
| D38999/29 | Lanyard Release Plug, Fail-Safe, Removable Crimp Contacts, Pins |
| D38999/30 | Lanyard Release Plug, Fail-Safe, Removable Crimp Contacts, Sockets |
| D38999/31 | Lanyard Release Plug, Fail-Safe, Pins, Shell Size 25 (MIL-STD-1760 Store Interface) |
| D38999/32 | Protective Cover, Plug (Series III Metric) |
| D38999/33 | Protective Cover, Receptacle (Series III Metric) |
| D38999/34 | Breakaway Receptacle, Jam-Nut Mounting, Sockets, Shell Size 25 |
| D38999/35 | Breakaway Receptacle, Wall Mounting Flange, Sockets, Shell Size 25 |
| D38999/36 | Lanyard Release Plug, Fail-Safe, Pins, Shell Size 25 |
| D38999/60 | Straight Plug, Removable Crimp Contacts, Fiber Optic Termini, Tight Tolerance, Shell Size 25 |
| D38999/61 | Wall Mounting Flange Receptacle, Removable Crimp Contacts, Fiber Optic Termini, Tight Tolerance, Shell Size 25 |
| D38999/62 | Sealing Boot, Size 8 Pin/Socket Shielded Crimp Contacts |
MIL-DTL-38999 Series IV
Series Characteristics & Key Features: Series IV connectors feature a quick-disconnect 90-degree breech-lock coupling mechanism. Specifically engineered for high-shock, extreme vibration, and SWAMP (Severe Wind and Moisture Problem) environments, they offer 100% scoop-proof protection along with tactile, visual, and audible locking confirmation. Covered under specification sheets D38999/40 through D38999/52.
| Specification Standard | Connector Style & Description |
| D38999/40 | Wall Mounting Flange Receptacle (Breech Coupling, Removable Crimp Contacts) |
| D38999/41 | Box Mounting Flange Receptacle (Hermetic, Breech Coupling, Hermetic Solder Contacts) |
| D38999/42 | Box Mounting Flange Receptacle (Breech Coupling, Removable Crimp Contacts) |
| D38999/43 | Jam-Nut Mounting Receptacle (Hermetic, Breech Coupling, Hermetic Solder Contacts) |
| D38999/44 | Jam-Nut Mounting Receptacle (Breech Coupling, Removable Crimp Contacts) |
| D38999/45 | Solder Mounting Receptacle (Hermetic, Breech Coupling, Hermetic Solder Contacts) |
| D38999/46 | Straight Plug with EMI Grounding Spring (Breech Coupling, Removable Crimp Contacts) |
| D38999/47 | Straight Plug without EMI Grounding Spring (Breech Coupling, Removable Crimp Contacts) |
| D38999/48 | Weld Mounting Receptacle (Hermetic, Breech Coupling, Hermetic Solder Contacts) |
| D38999/49 | In-Line Cable Receptacle (Breech Coupling, Removable Crimp Contacts) |
| D38999/50 | Dummy Stowage Receptacle (Breech Coupling, Series IV Metric) |
| D38999/51 | Protective Cover, Plug (Series IV) |
| D38999/52 | Protective Cover, Receptacle (Series IV) |
Summary Comparison Matrix Across Series
| Series | Coupling Mechanism | Scoop-Proof | Key Application / Advantage |
| Series I | 3-Pin Bayonet (1/4 turn) | Yes (100%) | General tactical duty, fast mating, contact protection |
| Series II | 3-Pin Bayonet (1/4 turn) | No (Low Profile) | Maximum space & weight savings, avionics, tight spaces |
| Series III | Triple-Start Thread (Self-Locking) | Yes (100%) | Extreme vibration, high temperature, SWAMP, EMI shielding |
| Series IV | Breech-Lock (90-Degree Turn) | Yes (100%) | Severe shock, missile launch systems, SWAMP areas |