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Maxx Model CNC Aluminum Hopup Chamber for M4 Airsoft AEG Rifles (Model: M4A - PRO)

ID: 102034 (HU-MX-MX-HOP010MA)
Maxx Model CNC Aluminum Hopup Chamber for M4 Airsoft AEG Rifles (Model: M4A - PRO)
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Hopup unit may require assembling
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Maxx Model Products


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  • Machined from a solid aircraft aluminum block with tight tolerances to provide better accuracy, consistency, and durability
  • Precision rotary dial design for fine hopup adjustments
  • Re-engineered the hopup levers and nubs to work best with R-hop, Flat-Hop and Standard-Hop to keep the BBs shooting straight and accurate on every single shot
  • Accepted the nozzle length from 21.00mm
  • Fully compatible with most aftermarket soft and hard rubber bucking without losing FPS or dropping BBs
  • Equipped with a new CNC Delrin Locking C-Clip design to hold barrel tight without wobbling and twisting, 3 compression springs on top, at bottom and in center of housing to ensure the hopup unit is exactly centered, straight and air tight
  • Compatible with any 11mm inner bore AEG Gearbox/HPA Engine nozzle outlets
  • Specially designed with BB Latching System to prevent dropping BBs after removing the magazine, manually opened to release BBs from inside hopup chamber by hand
CNC Aluminum Hopup Chamber M4A Pro (with BB Latching System) unit is precisely machined to perform accurately and consistently on Tokyo Marui (include G&G, KRYTAC, except KWA) Standard M4/M16 AEG series rifles.

The Hopup Chamber M4A unit is built with an aluminum rotary dial knob for fine hopup adjustments, the precision hopup lever and 4mm bucking nubs to perform best with R-Hop and standard-hop to keep the BB shooting accurately and consistently on every single shot.The Hopup Chamber M4A unit is designed to accept 21.00mm to 21.25mm nozzle length, and fully compatible with most aftermarket soft and hard rubber buckings without losing FPS or dropping BBs during use.

The Hopup Chamber M4A unit is wisely equipped with an interchangeable Inlet Adaptor OD11mm to ensure the hopup unit is inserted exactly in the center of the 11mm inner bore AEG Gearbox/HPA Engine nozzle outlet without wobbling. Also mounted the removable CNC brass side wings to slide smoothly into the outer barrel slots, and included an advanced CNC Delrin locking C-clip to hold the inner barrel tightly in place without wobbling and twisting.

Additionally, the Hopup Chamber M4A Pro unit is specially designed with a new BB Latching System to prevent BBs from dropping after removing the magazine. The Latching Arm can also be manually pressed to release the remaining BB from inside the hopup chamber.

Manufacturer: Maxx Model


Hopup Kit Includes:
  • 1 x CNC Aluminum Hopup Chamber M4A Pro (with BB Latching System) unit
  • 2 x CNC Acrylic Side Cover
  • 2 x CNC Brass 2.5mm Side Wing
  • 1 x CNC Steel Pivot Pin
  • 1 x CNC Aluminum Hopup Lever
  • 1 x CNC Aluminum Soft Round Nub
  • 1 x CNC Aluminum Soft Flat Nub (4mm)
  • 1 x CNC Aluminum Hard Concave Nub (4mm)
  • 3 x Steel Nub Spring
  • 1 x CNC Steel Spring Guide
  • 1 x Steel Upper Compression Spring
  • 1 x Steel Center Compression Spring
  • 1 x CNC Delrin Locking C-Clip
  • 1 x CNC Brass Barrel Spacer
  • 1 x Brass Barrel Spacer Holder O-ring
  • 1 x CNC Aluminum Rotary Dial Knob
  • 1 x CNC Aluminum Inlet Adaptor (OD11mm)
  • 1 x CNC Brass Inlet Spacer

  • Overall Length: 51.65mm
    Overall Height: 37.75mm
    Inlet Adaptor Outer Diameter (to fit into Gear Box): 11mm
    Hub Outer Diameter (to fit into Outer Barrel): 12mm
    Hub Inner Diameter (to fit Nozzle): 8mm
    Feeder Outer Diameter (to fit magazine): 8.85mm
    Feeder Length (to fit magazine): 6mm
    Application: For most Tokyo Marui (include KRYTAC, except KWA) M4/M16 standard AEG version 2 gear box
    Material: Aluminum 6061

    Test Results: FPS might be increased from 10FPS to 30FPS over the stock setup. Please check your FPS!
    Disclaimer: Professional installation highly recommended. Please use discretion when installing custom parts as fit and compatibility may vary. Modification may be required. Professional installation recommended.

    About Maxx Model Products

    Maxx Model Products design, manufacture, and make high quality parts for Airsoft products.

    6 Customer Reviews

    (Write a review)

    by June M. on 05/18/2024
    "Went into my A&K SR-25 build with no issues at all. I’m a big fan of the bb retention, AMS has a mag limit and every bb counts.
    by Joshua S. on 04/21/2024
    "Have an M4A in an AEG build and an M4P in an HPA Jack build and they are both great. Easy to install and make small adjustments.
    by Efrain V. on 09/04/2023
    "Review for M4i PRO

    I installed this in my ICS PCR-97 Olympic Arms M4. This is an older ICS M4 replica, while it does fit, some modification is required.
    I had to trim the large centering spring (spring that goes over inner barrel) I trimmed about a coil and a half to get the upper gearbox to fully seat.
    I had to buy a MAXX adjustable 19-22mm nozzle to get the bbs to properly feed (they were jamming against the stock nozzle due to length.

    I paired this with a Prommy EG barrel and Maple Leaf Macaron bucking. (bucking fit perfect, I had to slightly widen the c clip locking channel on the barrel to get the c clip to fully click into place (this probably is only a concern on the prommy eg barrels)

    After the modifications required to make this work in my ICS, I am very pleased with the results.
    This hop up is engineered so well and the build quality is excellent. Well worth the price in my opinion. I highly recommend this hop up.

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