NSN 1240-00-641-0657 · NIIN 006410657 · Part number 238518PC6
Navair and Navsea Managed Original Design Activity Dwg Not Material/parts Supplier · FSC 1240 — Optical Sighting and Ranging Equipment · FSG 12 — Fire Control Equipment · CAGE 10001
Government record, cited
NSN 1240-00-641-0657 — this item is cataloged by the U.S. Government under National Stock Number 1240-00-641-0657. Manufacturer of record part number: 238518PC6.
Also searched as1240-00-641-0657 ·
1240006410657 ·
NIIN 006410657 ·
00-641-0657 ·
FSC 1240 Optical Sighting and Ranging Equipment · CAGE 10001 · 238518PC6 · 3000042
Material Document and Classification: JAN-G-174, TYPE 517-645, GRADE C MIL SPEC SINGLE MATERIAL RESPONSE LOCATION NOT OTHERWISE SPECIFIED
Diameter: 49.000 MILLIMETERS NOMINAL MM
Reflection Reducing Surface: BOTH
Polished Periphery: NOT PROVIDED
Bevel Angle in Deg: 30.000 NOMINAL
Identification
NSN: 1240-00-641-0657
NIIN: 006410657
FSC: 1240 — Optical Sighting and Ranging Equipment
FSG: 12 — Fire Control Equipment
Primary part number: 238518PC6
Manufacturer: Navair and Navsea Managed Original Design Activity Dwg Not Material/parts Supplier
General Description
The Window,optical Instrument, cataloged under National Stock Number 1240-00-641-0657, is classified within Federal Supply Class 1240 (Optical Sighting and Ranging Equipment) of the Fire Control Equipment group. The manufacturer of record is Navair and Navsea Managed Original Design Activity Dwg Not Material/parts Supplier. Government technical data includes 11 specifications, cited from the U.S. Government catalog. The record lists 2 manufacturer part numbers for this item, enabling identification through both NSN and commercial part number lookups. 5 items share a part number with this NSN in the catalog (possible match — not a government interchangeability claim). Current acquisition status: Active.
Technical Specifications
Parameter
Value
NSN
1240-00-641-0657
Primary Part Number
238518PC6
Item Name
Window,optical Instrument
FSC / FSG
1240 / 12 — Optical Sighting and Ranging Equipment
Manufacturer
Navair and Navsea Managed Original Design Activity Dwg Not Material/parts Supplier
Status
ACTIVE
FSC Application Data
TELESCOPE MK 77 MOD 0
Bevel Depth
3.750 MILLIMETERS NOMINAL MM
Material Document and Classification
JAN-G-174, TYPE 517-645, GRADE C MIL SPEC SINGLE MATERIAL RESPONSE LOCATION NOT OTHERWISE SPECIFIED
Diameter
49.000 MILLIMETERS NOMINAL MM
Reflection Reducing Surface
BOTH
Polished Periphery
NOT PROVIDED
Bevel Angle in Deg
30.000 NOMINAL
Material
GLASS OPTICAL LOCATION NOT OTHERWISE SPECIFIED
Refraction Index
1.5171 NOMINAL
Polished Surface
BOTH
Thickness
5.000 MILLIMETERS NOMINAL MM
Lifecycle & Compliance
Acquisition Status
ACTIVE
DEMIL Code
DEMIL D — Destroy Item
Hazard
No hazard code in the DLA record (HMIC N)
Criticality Code
X
⇄Related Items5
Each row states its source: a government interchangeability/replacement code, or a possible match on a shared part number.
5840-01-469-1287300004-2POSSIBLE MATCH
CONTROL,LOCAL
Possible match (shared part number)Northrop Grumman Systems Corporation
5305-01-579-80613000042-025050POSSIBLE MATCH
SCREW,CAP,SOCKET HEAD
Possible match (shared part number)Bae Systems Land & Armaments L.p.
5305-01-579-80713000042-025062POSSIBLE MATCH
SCREW,CAP,SOCKET HEAD
Possible match (shared part number)Bae Systems Land & Armaments L.p.
5305-01-613-10363000042-025075POSSIBLE MATCH
SCREW,CAP,SOCKET HEAD
Possible match (shared part number)Bae Systems Land & Armaments L.p.
5305-01-613-10603000042-050075POSSIBLE MATCH
SCREW,CAP,SOCKET HEAD
Possible match (shared part number)Bae Systems Land & Armaments L.p.
Navair and Navsea Managed Original Design Activity Dwg Not Material/parts Supplier (USA)
Related Parts
5840-01-469-1287POSSIBLE MATCH
CONTROL,LOCAL
300004-2
5305-01-579-8061POSSIBLE MATCH
SCREW,CAP,SOCKET HEAD
3000042-025050
5305-01-579-8071POSSIBLE MATCH
SCREW,CAP,SOCKET HEAD
3000042-025062
5305-01-613-1036POSSIBLE MATCH
SCREW,CAP,SOCKET HEAD
3000042-025075
5305-01-613-1060POSSIBLE MATCH
SCREW,CAP,SOCKET HEAD
3000042-050075
Frequently Asked Questions
What is NSN 1240-00-641-0657?
NSN 1240-00-641-0657 is a Window,optical Instrument, manufactured by Navair and Navsea Managed Original Design Activity Dwg Not Material/parts Supplier, classified under FSC 1240, Optical Sighting and Ranging Equipment. Status: active.
What part numbers are listed for NSN 1240-00-641-0657?
NSN 1240-00-641-0657 has 2 manufacturer part numbers on file: 238518PC6 (Navair and Navsea Managed Original Design Activity Dwg Not Material/parts Supplier), 3000042 (Navair and Navsea Managed Original Design Activity Dwg Not Material/parts Supplier).
What NSN replaces 1240-00-641-0657?
5 possible matches (shared part number, not a government interchangeability claim): 5840-01-469-1287, 5305-01-579-8061, 5305-01-579-8071. Verify interchangeability with system specifications before substitution.
What are the specifications of 238518PC6?
Key specifications for 238518PC6: FSC Application Data: TELESCOPE MK 77 MOD 0; Bevel Depth: 3.750 MILLIMETERS NOMINAL MM; Material Document and Classification: JAN-G-174, TYPE 517-645, GRADE C MIL SPEC SINGLE MATERIAL RESPONSE LOCATION NOT OTHERWISE SPECIFIED; Diameter: 49.000 MILLIMETERS NOMINAL MM. 11 specifications are documented in the U.S. Government catalog.
Is NSN 1240-00-641-0657 hazardous material?
No hazard code in the DLA record (HMIC N). Hazard information on this page is shown exactly as it appears in the DLA record.
What is the DEMIL code for NSN 1240-00-641-0657?
NSN 1240-00-641-0657 has DEMIL Code D. Demilitarization may be required before disposal or transfer to non-military entities.
Sources
U.S. Government catalog: edition PUBLOGDVD v12.0.0 (OCT 2026), edition date 2026-10-01, retrieved 2026-10-16.
U.S. Government catalog: edition PUBLOGDVD v12.0.0 (OCT 2026), edition date 2026-10-01, retrieved 2026-10-18.
✓ Data cited from the U.S. Government catalog; commercial cross-references from OEM and certified industry sources.