HK HAUS
HK HAUS
  • HOME
  • PISTOLS
    • P7
    • P8
    • P10
    • P12
    • P30
    • USP
    • Mark 23
    • HK 45
    • HK 45C
    • MK24 Mod 0
    • P2000 & P2000 SK
    • VP9 & VP9 SK
    • SFP9
    • SFP9 OR MATCH
    • SFP9 CC
  • SMG
    • MP7
    • UMP
    • MP5
  • RIFLES
    • HK433
    • HK437
    • HK416
    • HK417
    • G36
    • G3
    • PSG1
  • MACHINE GUNS
    • MG4
    • MG5
    • HK21
  • 40 MM
    • GLM
    • HK169
    • HK269
    • GMG
  • TECHNICAL
    • ABREVIATIONS
    • NUMERIC AND DATE CODES
    • PROOF MARKS
    • HK OPERATOR'S MANUALS
    • HK TRIGGER GROUPS
    • HK416 RECEIVER EXTENSIONS
    • HK MR FIRE CONTROL
    • HK SA80 MARITIME MAGAZINE
  • HISTORY
  • HAUS
  • More
    • HOME
    • PISTOLS
      • P7
      • P8
      • P10
      • P12
      • P30
      • USP
      • Mark 23
      • HK 45
      • HK 45C
      • MK24 Mod 0
      • P2000 & P2000 SK
      • VP9 & VP9 SK
      • SFP9
      • SFP9 OR MATCH
      • SFP9 CC
    • SMG
      • MP7
      • UMP
      • MP5
    • RIFLES
      • HK433
      • HK437
      • HK416
      • HK417
      • G36
      • G3
      • PSG1
    • MACHINE GUNS
      • MG4
      • MG5
      • HK21
    • 40 MM
      • GLM
      • HK169
      • HK269
      • GMG
    • TECHNICAL
      • ABREVIATIONS
      • NUMERIC AND DATE CODES
      • PROOF MARKS
      • HK OPERATOR'S MANUALS
      • HK TRIGGER GROUPS
      • HK416 RECEIVER EXTENSIONS
      • HK MR FIRE CONTROL
      • HK SA80 MARITIME MAGAZINE
    • HISTORY
    • HAUS
  • Sign In
  • Create Account

  • My Account
  • Signed in as:

  • filler@godaddy.com


  • My Account
  • Sign out

Signed in as:

filler@godaddy.com

  • HOME
  • PISTOLS
    • P7
    • P8
    • P10
    • P12
    • P30
    • USP
    • Mark 23
    • HK 45
    • HK 45C
    • MK24 Mod 0
    • P2000 & P2000 SK
    • VP9 & VP9 SK
    • SFP9
    • SFP9 OR MATCH
    • SFP9 CC
  • SMG
    • MP7
    • UMP
    • MP5
  • RIFLES
    • HK433
    • HK437
    • HK416
    • HK417
    • G36
    • G3
    • PSG1
  • MACHINE GUNS
    • MG4
    • MG5
    • HK21
  • 40 MM
    • GLM
    • HK169
    • HK269
    • GMG
  • TECHNICAL
    • ABREVIATIONS
    • NUMERIC AND DATE CODES
    • PROOF MARKS
    • HK OPERATOR'S MANUALS
    • HK TRIGGER GROUPS
    • HK416 RECEIVER EXTENSIONS
    • HK MR FIRE CONTROL
    • HK SA80 MARITIME MAGAZINE
  • HISTORY
  • HAUS

Account


  • My Account
  • Sign out


  • Sign In
  • My Account

HK416 VS MR556 RECEIVER EXTENSION COMPARISON

The receiver extension on top is an HK416 A1 HK spec tube and the one on the bottom is an MR556 mil-spec. As you can see here, the commercial spec extension is longer than the mil-spec extension.

HK416 A1 Receiver Extension VS HK MR556 A1 Mil-Spec Receiver Extension

HK416 A1 HK spec Buffer Tube


Length - 199.07mm or 7.834”


Diameter - 29.68 or 1.167”


Top to bottom measurement - 37.20 or 1.466


Weight - 144.5 grams or 5.10 oz




HK Mil Spec Buffer Tube


Length - 183.12 or 7.209”


Diameter - 29.07mm or 1.145”


Top to bottom measurement - 36.91 or 1.453


Weight - 104.1 grams or 3.67 oz


The receiver extension on top is an HK416 A1 HK spec, the bottom one is a mil-spec MR556.

HK 416 A1 Receiver Extension VS HK416 A5 Receiver Extension

HK416 A1 tube


Length - 199.07mm or 7.834”


Width - 29.68 or 1.167”


Top to bottom measurement - 37.20 or 1.466


Weight - 144.5 grams or 5.10 oz




HK416 A5 tube


Length - 199.07mm or 7.834”


Width - 29.68 or 1.167”


Top to bottom measurement - 37.20 or 1.466


Weight - 143 grams or 5.5 oz


The receiver extension on top is an HK416 A1, the bottom is an HK416 A5.

A5 vs A1

Each of these receiver extensions have a raised area on the bottom that acts as a stop and prevents the castle nut from turning counterclockwise once it reaches a certain point, indicated here by the red arrows. 

This is important because the newer extended style castle nuts are much larger and without adequate room to back the castle nut off, the buffer retainer assembly cannot be installed. As a result the extended style castle nut cannot be used with the A1 style HK spec receiver extension.

Copyright © 2025 HAUS MANUFACTURING LLC

Powered by