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Questions & Answers
what length gas system does this upper have? carbine, mid or rifle? Manufacturer Answer

The Luth-AR Mark 12 barrels will have a rifle length gas system.

by Luth-AR, Manufacturer, January 2, 2025
what does "need GT-CUP" mean? Manufacturer Answer

If you want to attach a push button sling swivel to the stock you will need a Grovtec threaded base cup sold at Optics Planet under that product code number GT-CUP.

by Luth-AR, Manufacturer, January 2, 2025
Customer Reviews
Helpful Positive Review Luth-AR-15 Complete by Chad, October 30, 2019
Ordered and received on time. Everything was in perfect condition. put everything on my lower and went and shot. No problems what so ever. top-notch barrel and receiver. the bolt is military-grade. Will purchase another.
3/3 found this helpful
Most Recent Reviews Overall Impressed by Mick, Verified Owner, May 7, 2022
Unboxing review: Items were packaged properly and securely. There was no excessive packing grease, YAY! All parts were in good condition including the bolt and bolt carrier. The bore of the barrel was clean and the grooves looked flawless to the nake...
Read More...
Most Recent Reviews Very Nice! by IOVVOI, Verified Owner, April 30, 2022
Bought this for my first AR build and I gotta say was very pleased with Luth-AR 5.56 Complete MARK12 Barrel Kit. Shipping was fast and packaged nicely. Comes with the MBA3 stock, which btw looks and feels right because, of the adjustments one can mak...
Read More...
Read All 3 Reviews
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Product Info for Luth-AR 5.56 Complete Mark 12 Barrel Kit

The Luth-AR 5.56 Complete Mark 12 Barrel Kit features an 18 inch Mark 12 5.56mm barrel and a 15in KeyMod short mid-length rail, so you can build a customized upper to add onto your stripped lower receiver. These AR15 Upper Receivers by Luth-AR are built tough with 4140 Chrome Moly steel with a 1-9 twist rate to ensure the accuracy you need from your rifle. This Luth-AR 5.56 Complete Mark 12 Barrel Rifle Upper Receiver Kit is also designed with 6 lands and groves, so you can use a variety of accessories and optics with this barrel. Button broaching adds extra strength and prevents the parts from corroding over time. You can also mount a suppressor or any other device you desire with this kit. The Luth-AR 5.56 Complete Mark 12 Barrel Mid-Length RH Barrel Kit features an attachment rail on the handguard, so you can easily install an A2 flash suppressor or other device that requires a mountable rail.image

Specifications for Luth-AR 5.56 Complete Mark 12 Barrel Kit:

Manufacturer: Luth-AR
Caliber: .223 Remington, 5.56x45mm NATO
Overall Length: 27 in
Barrel Length: 18 in
Stock/Brace Material: 4140 Chrome-Moly Steel
Barrel Profile: Government
Gas System Length: Rifle Length
Barrel Twist Rate: 1-9
Number of Sling Points: 2
Threads per Inch: 1/2x28
Handguard Type: Free-Float
Muzzle Device: A2 Flash Hider
Finish: Manganese Phosphate
Color: Black
Gun Model: AR-15
Fabric/Material: 4140 Chrome Moly
Gas Block Journal Size-Diameter: .750 in
Handguard Length: 15 in
Handguard Style: Round Rail
Gun Rail: KeyMod
Gun Type: Rifle
Gun Make: AR Platform
Additional Features: Will need GT-CUP
Bolt Carrier Group Included: MIL-SPEC
Charging Handle Included: MIL-SPEC
Weight: 12 lb, 11 lb
Magazine Included: No

Features of Luth-AR 5.56 Complete Mark 12 Barrel Kit

  • Upper Specs:
    • 7075-T6 Forging
    • Hardcoat anodize Black
  • Bolt Specs:
    • Bolt: Carpenter 158 steel
    • Extractor: 4140 Alloy steel
    • Army Spec Heat Treatment
    • Manganese Phosphate
  • Bolt Carrier Specs:
    • Carrier: 8620 steel
    • Cam pin: 4340 Alloy steel
    • Carrier key: 4130 Alloy steel
    • Army Spec Heat Treatment
    • Manganese Phosphate
  • Barrel Specs:
    • 18″ Mark 12 5.56 mm Barrel
    • 5.56 mm
    • 4140 Chrome Moly
    • Threaded Barrel - Thread Pitch 1/2 x 28
    • 1-9 RH Barrel Twist
    • 6 Lands and Grooves
    • M4 Feed Ramp
    • Button Broached

Package Contents:

  • Luth-AR 5.56 Complete Mark 12 Barrel Kit
  • Fully assembled Mark 12 5.56mm Upper with 15in Keymod Palm Handguard
  • Buttstock Assembly (Black)- Fixed Buttstock OR Collapsible Buttstock
    • MBA-1 Fixed Rifle Buttstock Assembly
    • MBA-3 Adjustable Carbine Buttstock Assembly
  • Complete Lower Parts Kit (LRPK-1 Complete .223/5.56 Lower Receiver Parts Kit)
  • Includes:
    • BAA3-M12 - 18″ Mark12 5.56 mm Barrel
    • BC-A-223 - Fully Assembled Bolt Carrier
    • BL-04 - Standard Gas Tube
    • BL-06-A2 - A2 Flash Hider
    • FTT-EA1 - A3 Upper Receiver Assembled
    • GB-LP750 - Gas Block .750
    • HG-V-15K - Palm Handguard® - Vented 15″ KeyMod/MLOK/Smooth with Barrel NutFeatures of Luth-AR AR-15 Complete MARK 12 Barrel Kit

Luth-AR 5.56 Complete Mark 12 Barrel Kit Orderable Models

List of Orderable Models

Luth-AR Mark 12 Kit Minus Lower Receiver, w/ Collapsible Stock, 5.56mm, 27in, 18in, Government, Rifle, 1x9, 1/2x28, Picatinny, Key MOD, A2 Flash Hider, Anodized, Manganese Phosphate, Black, RKM12-18-3 , MPN: RKM12-18-3 , UPC: 812058030560 , Code: 3FN-UFH-AR15C18M12F-RKM12-18-3
Luth-AR Mark 12 Kit Minus Lower Receiver, w/ Fixed Stock, 5.56mm, 27in, 18in, Government, Rifle, 1x9, 1/2x28, Picatinny, Key MOD, A2 Flash Hider, Anodized, Manganese Phosphate, Black, RKM12-18-1 , MPN: RKM12-18-1 , UPC: 812058030553 , Code: 3FN-UFH-AR15C18M12F-RKM12-18-1
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