MIL-C 38999 Series I,II,III,IV

MIL-DTL-38999 (originally MIL-C-38999) Connector

Standard and High Density, multi-pin, lightweight, miniature military circular connectors.



For all military and aeronautical purposes, tactical missiles, fighting vehicles. instrumentation (Series II) and control, etc. The MIL-DTL-38999 (originally MIL-C-38999) specification covers four series of miniature, high density, bayonet, threaded, or breech coupling, circular, environment resistant, electrical connectors using removable crimp or fixed hermetic solder contacts, and are capable of operation within a temperature range of -65°C to +200°C.

All series include rear release removable pin and socket contacts with crimp termination. All series are designed to assure proper orientation of the mating halves prior to electrical circuit closure. All series include hermetically sealed receptacles with fixed contacts for solder termination. All series include EMI shielding capability. Series I, III, and IV connectors with conductive finishes provide electrical continuity between mated shells prior to contact engagement and have the contacts so located as to be protected from handling damage and inadvertent electrical contact. Series II provides low silhouette for minimum size and weight and includes connectors which provide shell-to-shell electrical continuity when mated

Key Features

Key Features

  • Conform to MIL-DTL-38999 (originally MIL-C-38999)
  • BS9520 G0003
  • Quick disconnect bayonet or triple thread coupling for positive mating in 360º turn.
  • 9 shell sizes,
    Series I & III – 9 through 25
    Series II – 8 through 24
  • Positive metal to metal coupling for excellent EMI shielding
  • Locksmith keying orientation (machined into shell)
  • Crimp contacts to MIL-C-39029, sizes 22D, 20, 16 & 12
  • Up to 128 contacts (22D)
  • All Series share common insert arrangements accepting mixed layout or coaxial/triaxial contacts
  • Fluorosilicone interfacial ‘environmental’ seal between contacts and shell
  • Chamfered conical entry to interfaces to aid proper mating of contacts
  • Filtered types available.
  • D38999 connectors are also available in a wide range of finishes and shell materials including anodic, zinc cobalt, aluminum, electroless nickel, olive drab cadmium and more.

An extensive range of Backshells to suit D38999 connectors are available to order separately




  • Shell
    Normal – Aluminium alloy, plated olive drab cadmium, black anodized or nickel.
    Hermetic – Steel, stainless steel & passivate or nickel.
    Sizes – Series II – 08, 10, 12, 14, 16, 20, 24.
    Series I & III – 09, 11, 13, 15,17, 19, 21, 23, 25
  • Insulator
    Normal – Thermoplastic fluoronated silicone elastomer.
    Hermetic – Sintered glass insert.
  • Insulator
    Contacts – Gold or gold/tin lead over copper alloy or nickel.
    Crimp / PC tail ~ 3 to 128 Male or Female.
    Accept 12 to 28 AWG terminating wire sizes

Coaxial contact # 8 for RG 180B/U, RG 195A/U


  • Current
Size Normal Hermetic Volt Drop
22D 5.0A 3.0A 73 millivolt max
20 7.5A 5.0A 55 millivolt max
16 13.0A 10.0A 49 millivolt max
12 23.0A 17.0A 42 millivolt max
  • Test voltage V rms
Service Sea Level 21000m Unmated
M 1300 800 350
I 1800 1000 400
II 2300 1000 500
  • Contact Resistance
22D 14.6 M
20 7.3 M
16 3.8 M
12 1.7 M
  • Insulation Resistance – > 5,000 M at 500 Vdc
  • Shielding 90 dB to 100 MHz.
    50 dB to 10,000 MHz.


  • Contact to insulator holding force.
    22D – 45 N
    8 – 110 N
  • Mechanical operations – 500 Min
  • Vibration: – sine 10 to 2000Hz 30g.
    – random 100 to 300 Hz 5 g²/Hz.
  • Physical shocks – 300g. 3ms in the 3 axes


  • Working temperature :
    Cadmium plated -55 to +125ºC.
    Nickel plated -65 to +200ºC.
  • Resistance to salt spray:
    Normal plating 500 hours per. MIL-STD 1344 method 1001, test B & NFC 93422.
    Nickel plated – 48 hours.
  • Damp Heat: MIL-C-38999 – 10 cycles 24 hours.
  • Sealing: Mated connector < 16 cm3/hr under a differential pressure of 2.1 bar.
  • Thermal shock: as MIL-C 38999 para. 3-7, 3-8.


  • Series 1
    MS 27466 – Wall mount receptacle
    MS 27467 – Straight plug with EMI grounding
    MS 27468 – Jam nut receptacle
    MS 27469Y – Hermetic wall mount receptacle
    MS 27470Y – Hermetic jam nut receptacle
    MS 27471Y – Hermetic solder mount receptacle
    MS 27496E – Box mount receptacle
    MS 27505E – Box mount receptacle, rear panel mounting
    MS 27656 – Wall mount receptacle, rear panel mounting
    MS 27661 – Straight plug, lanyard release
    MS 27662E – Through bulkhead receptacle
  • Series 2
    MS 27472 – Wall mount receptacle
    MS 27473 – Straight plug
    MS 27474 – Jam nut receptacle
    MS 27475Y – Hermetic wall mount receptacle
    MS 27476Y – Hermetic box mount receptacle
    MS 27477Y – Hermetic jam nut receptacle
    MS 27478Y – Hermetic solder mount receptacle
    MS 27497 – Wall mount receptacle, back panel mounting
    MS 27499E – Box mount receptacle
    MS 27508E – Box mount receptacle, back panel mounting
    MS 27513E – Box mount receptacle, long grommet
  • Series 3
    D38999_20 – Wall mount receptacle
    D38999_21 – Hermetic sealed box mount receptacle
    D38999_23 – Hermetic sealed jam nut receptacle
    D38999_24 – Jam nut receptacle
    D38999_25 – Hermetic sealed solder mount receptacle
    D38999_26 – Straight plug
    D38999_27 – Hermetic sealed weld mount receptacle
    D38999_29 – Lanyard release plug, pin contacts
    D38999_30 – Lanyard release plug, socket contacts
  • Series 4
    D38999_40 – Wall mount receptacle
    D38999_41 – Hermetic box mount receptacle
    D38999_42 – Box mount receptacle
    D38999_43 – Hermetic jam nut receptacle
    D38999_44 – Jam nut receptacle
    D38999_45 – Hermetic solder mount receptacle
    D38999_46 – Straight plug with EMI grounding
    D38999_47 – Straight plug
    D38999_48 – Hermetic weld mount receptacle
    D38999_49 – In-line receptacle


MIL-DTL-38999 (MIL-C-38999) Series I

High Density bayonet connectors, “scoop proof” crimp rear release contacts. MIL-DTL-38999 Series I Connectors are a bayonet coupling subminiature configuration with high contact density for harsh-environment applications. These environment-resisting connectors are 100% scoop-proof. Pins are recessed in elongated shells to prevent the possibility of bending contacts when plugs are scooped into the mating receptacles.

MIL-DTL-38999 (MIL-C-38999) Series II

Bayonet connectors, “low profile”, crimp rear release contacts. These connectors were designed for military and commercial applications where the prime requirements are lower profile and lighter weight. Reduction of both size and weight is achieved through the use of thinner shell walls and shorter bodies. These design restrictions reduce the RFI attenuation characteristics and eliminate the scoop protection, but produce an excellent general-purpose, lightweight connector. Compared with MIL-C-38999 Series I, Series II connectors achieved up to 20% reduction in mated pair length, up to 39% reduction in outside diameter and up to 40% reduction in weight

MIL-DTL-38999 (MIL-C-38999) Series III

Triple start thread “vibration resist” connectors, crimp rear release contacts. “Scoop proof” with ‘Metric’ accessory threads for greater strength and support of backshells.

MIL-DTL-38999 (MIL-C-38999) Series IV

Breech lock, quick disconnect connectors, crimp rear release. Breech-Lok, Series IV connectors feature a coupling mechanism that only requires 90° of rotation to engage and disengage. This rugged design distributes the coupling load over solid-metal lands while internal-drive threads provide the mechanical advantage needed to ensure positive engagement of the contacts and interfacial seals.

The above four Series are NOT intermateable with each other.

Amphenol have introduced the High Density HD38999 family of connectors to work with existing mil-specified 38999 shells. To end users familiar with standard 38999 connectors, this family of high density connectors will look, feel, and perform just like the mil-qualified connectors. Utilizing an existing mil-qualified 39029 size 23 contact and mil-qualified shells, the new system is usually a drop-in connector. Even though the HD38999 has 30% more contacts, it still performs to minimum electrical requirements of standard 38999 connectors. HD38999 are available with from 9 to 187 contacts.