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Laevateinn 300BLK Upper

Laevateinn 300BLK Upper


The Laevateinn Complete Upper Receiver Manufactured by Eitri’s Enhancements, LLC




The final culmination of 3 years of research and development into the 6” 300Blk barrel with a pistol length gas system.


We finally bring a reliable platform capable of competing with the best.

  • Description

    This complete upper goes through our eyes and hands to ensure every precautionary step of the assembly process is monitored, and performed.

    If you know us, you know we are suckers for everything technical, we like to dive deep into every potential outcome or solution, with simplicity always in mind.

    As such, no detail or part was overlooked, every component on this platform has been micro-analyzed and is currently present due to its particular benefits in terms of efficiency, cost, maintenance and reliability.

    The BCG we use in each upper is inspected for efficiency and are only used if they pass all of our requirements

    The Laevateinn is built with commonly found automotive processes which include:

    Full gasket sealing of all non-interference-fit gas system components.

    Gas system port matching.

    Gas flow channels and pathways meticulously inspected for internal dimensions to prevent flow restrictions.

    All moving components coated for friction reduction.

    Spring rates adapted to match each specific component based on application

    Mass reduction to components for improved energy transfer and synchronization.

    Fuel system analysis and understanding for efficient gas system operation.

  • Included with Upper

    • Sprinco Yellow Buffer Spring
    • Reduced-Drag Hammer Spring
    • B.A.D. High-Speed Bolt Catch
  • Specifications:

    BCG Specs:

    Manufacturer: Microbest

    Bolt: C158 MPI/HPT (MPI markings only)

    Springs: Sprinco 5-coil extractor, Microbest Ejector Spring (Stronger than Sprinco)

    Cam Pin: FCD Sotar NP3 Coated

    BCG Coating: Chrome



    Manufacturer: Faxon

    Caliber: 300BLK

    Length: 6”

    Caliber: 300blk

    Material: 416R stainless steel

    Rifling: 1/5 Twist (5R)

    Barrel extension: NP3 Coated

    Gas System: Pistol

    Thread Pitch: 5/8x24


    Gas block:

    Manufacturer: VLTOR

    Type: Clamp-On

    Securement Method: Screws torqued to 30in-lbs wet with blue loctite and staked in place

    Sealant: Permatex No3

    Fitment: Gas tube is reamed out to perfectly match gas block port diameter for increased flow.



    Length: 5.25”

    Type: Free float with M-Lok


    Charging Handle:

    Manufacturer: Geissele

    Type: Airborne (ACH)


    Upper Receiver:

    Type: Mil-Spec Slick Side

    Ejection Port Cover: Mil-Spec

    Weight: 2lbs 12.5oz (Complete Upper without extra included parts)

    Length: 14.75"


  • Requirements for Use

    All extra components included MUST be used with this upper in order to ensure reliable function.


    We only recommend the use of Magpul 300blk Pmags with this upper.


    The buffer spring included is only designed to work with standard/mil-spec length carbine buffers/tubes. We recommend the use of a carbine buffer which weighs anywhere between 1-3oz. your suppressor choice may dictate your needs (an empty buffer weighs 1oz) 


    We only recommend the use of the included hammer spring with a 2-stage trigger such as Geissele, Larue, or Schmid Tool. Use of this spring with a mil-spec trigger may or may not require the hammer to be "bobbed" or modified to reduce mass in order to prevent light strikes.

  • Terms and Conditions:

    Eitri’s Enhancements, LLC is not responsible for any property damage, physical damage, bodily injury, or bodily harm caused by use of its products or services. Customer, by paying the purchase price of this item, agrees that he or she shall be solely responsible for any such harm that may occur from the use of any Eitri’s Enhancements, LLC product or service. Customer also warrants that they have read, reviewed, and fully understand how to operate any product purchased from, serviced, and/or manufactured by Eitri’s Enhancements, LLC.

  • Suppressor Use Requirements

    Must be used with a "Baffled" suppressor in order to ensure subsonics function in this platform.

    It is possible to use a "flow-through" suppressor but you will be depriving the system of the extra backpressure required to run all available subsonics

  • Subsonics Un-Suppressed Info

    Yes! This upper can run un-suppressed subsonics! 

    HOWEVER, without the suppressor your available ammunition which is capable of cycling the upper will be severely diminished.

    IF you plan on using this upper un-suppressed with sub-sonic ammunition , you will need to use ammunition which contains Accurate 1680 or CFE BLK powder in order to maintain full function. (it is virtually impossible to know which ammunition manufacturers use these powder so "reloading" may be your only option to achieve function in this configuration)

  • 100% Payment VS 50% Payment

    Customer may purchase this product at 100% cost or 50% cost. Either option will begin the assembly process of the order.

    If customer selects the 50% initial payment option. The remaining 50% will be due upon product completion.

    Customer will receive final 50% invoice via email to complete the purchase once the product is complete.

    Customer understands that the product will not ship until the final 50% payment is submitted.

  • Refund Policy

    Product can be fully refunded during the first 7 days after purchase with a 5% re-stocking fee.

    After the first 7 days, refund can be issued with a 20% re-stocking fee.

    Once the the product is assembled and ready to ship, refunds can no longer be issued. 

    If 50% initial payment is selected, the product will not ship until the final 50% payment is submitted. There will be no refunds of the initial 50% payment once the product is assembled.

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