5KU 5-Positions Stock Tube for M4 AEG

The 5KU 5-Position Stock Tube for M4 AEG is a metal buffer tube for M4 AEG airsoft replicas with an adjustable stock. With five locking positions, you can adjust the length of your replica to suit your build, shooting stance and equipment. The stock tube is finished in black and has a total length of 165 mm.

This 5KU stock tube is designed to replace an existing buffer tube or for an M4 AEG build where you wish to fit an adjustable stock. The metal construction provides a sturdy base for the stock. It also comes with a fixing screw and a shim, so you have all the necessary mounting materials.

Why choose the 5KU 5-Position Stock Tube for M4 AEG?

An adjustable stock is only practical if the underlying buffer tube fits your replica and the desired stock properly. The 5KU 5-Position Stock Tube offers five fixed adjustment positions, allowing you to adjust the length of the stock to suit different situations.

In airsoft, this can be particularly useful when you alternate between playing with light kit and a plate carrier. A shorter stock position can be more comfortable when you’re carrying a lot of gear on your chest, whilst a longer position may feel more comfortable with a different shooting stance.

The 5KU has been specifically developed for M4 AEG platforms and comes with the necessary fixing screw and shim.

Five adjustment positions for your M4 stock

The stock tube has five positions in which a suitable adjustable stock can be secured. This allows you to adjust the distance between the shoulder rest and the rest of your replica.

The ideal setting depends on your build, arm length and equipment. For example, a player wearing a plate carrier may find a different stock position more comfortable than someone wearing only a battle belt.

The actual adjustment range also depends on the type of stock you fit to the tube.

Metal structure

The 5KU stock tube is made from metal. This makes it suitable for use as a structural mounting component for an adjustable M4 AEG stock.

During use, a stock tube is regularly subjected to stress caused by shouldering and moving the replica. Correct fitting is therefore just as important as the material itself.

When installing, ensure that the tube is securely fastened and that the barrel moves over the tube without excessive play.

Designed for M4 AEG replicas

This version is designed for M4 AEG airsoft replicas. This distinction is important, as buffer tubes for AEG, GBB and other AR platforms may differ in terms of mounting and dimensions.

The 5KU-77 is explicitly designated by the supplier as AEG Series Only. It is therefore unwise to assume that this tube will also fit an M4 GBBR or any other system.

Even within M4 AEG platforms, manufacturers may use different fastenings and tolerances. You should therefore always check the existing assembly before ordering parts.

Total length of 165 mm

The stock tube has a specified length of 165 mm. This measurement is useful if you want to compare the 5KU with the stock tube currently fitted to your replica.

The length of the barrel does not automatically determine the overall length of your replica. This also depends on the stock fitted and the adjustment position chosen.

When replacing a tube, therefore, check both the length of the existing tube and the connection to the receiver.

Compatibiliteit met MILSPEC- en COMSPEC-stocks

When combining a stock tube with an adjustable stock, the outer diameter of the tube is an important consideration. Stocks are often marketed as MILSPEC or COMSPEC versions, but not every airsoft manufacturer uses exactly the same dimensions.

M4 AEG systems from manufacturers such as Tokyo Marui, VFC and G&G are often associated with dimensions that are closer to MILSPEC. However, this does not mean that every stock from these brands will fit onto every AEG buffer tube without any play.

No exact outer diameter has been confirmed for the 5KU-77. We are therefore unable to classify this stock tube as MILSPEC or COMSPEC without reservation.

If in doubt, measure the existing tube and check the internal dimensions of the stock you wish to use. Bear in mind that minor manufacturing variations may affect the fit.

Suitable for replacement and custom builds

The 5KU 5-Position Stock Tube is a good option if your existing buffer tube is damaged or if you want to use a different adjustable stock on your M4 AEG.

Even with a custom build, a separate stock tube can be useful. This allows you to tailor the stock design to your own preferences, provided that the connection to the receiver and the chosen stock are compatible.

The barrel is supplied without a stock. This means you can choose a suitable adjustable M4 stock yourself.

Includes fixing screw and shim

This stock tube comes with a buffer tube adapter screw and shim. These are parts used when fitting the tube.

That’s handy when you’re replacing an existing stock tube and don’t want to be entirely reliant on reusing old fixing parts.

Whether the parts supplied will fit your replica directly depends on the design of the receiver and the internal mounting system used.

Black version

The stock tube is finished in Black. This means it matches most black M4 AEG receivers and adjustable tactical stocks.

Its neutral colour also makes it easy to combine with various stock models and airsoft loadouts.

Practical tip

Before ordering, check three things: the mounting of your current buffer tube, the outer diameter of the tube and the internal diameter of the stock you wish to fit. A stock that is too loose may move or rattle, whilst one that is too tight may be difficult or impossible to slide over the tube. Therefore, do not rely solely on the ‘M4 compatible’ label.

In the box

When you purchase the 5KU 5-Position Stock Tube for M4 AEG, you will receive:

　• 5KU 5-Positions Stock Tube for M4 AEG
　• Buffer tube adapter screw
　• Shim

Please note: an adjustable stock is not included.

Specificaties

　• Merk: 5KU
　• Product: 5-Positions Stock Tube for M4 AEG
　• Artikelnummer: 5KU-77
　• Type: Buffer tube / stock tube
　• Platform: M4 AEG
　• Compatibiliteit: AEG Series Only
　• Materiaal: Metaal
　• Kleur: Black
　• Totale lengte: 165 mm
　• Aantal verstelposities: 5
　• Kaliber replica: 6 mm airsoft
　• Bevestigingsschroef: Inbegrepen
　• Shim: Inbegrepen
　• Verstelbare stock: Niet inbegrepen
　• MILSPEC/COMSPEC: Niet officieel bevestigd
　• Buitendiameter: Niet opgegeven
　• Geschikt voor: Vervanging of montage van een verstelbare stock op compatibele M4 AEG-replica's

Frequently Asked Questions

Does this stock tube fit any M4 AEG?

No, we cannot guarantee that. The tube is designed for M4 AEG replicas, but manufacturers sometimes use different mounting points and tolerances. You should therefore compare the connection on your current stock tube with this version before ordering.

Can I use my existing M4 stock on this tube?

That depends on the internal dimensions of your stock and the external diameter of the tube. Not every M4 stock has exactly the same fit. It is particularly important to check the dimensions for MILSPEC and COMSPEC versions. A well-fitting stock should be easily adjustable without excessive play.

Is this buffer tube suitable for an M4 GBBR?

This version is specifically designed for AEG systems. For an M4 GBBR, we recommend choosing a buffer tube that has been specifically developed for the relevant gas blowback platform.

Can I fit the battery from my M4 AEG into this stock tube?

That is not guaranteed. Whether a battery will fit in the buffer tube depends on the internal space, the wiring, the connector and the battery’s dimensions. No usable internal diameter has been specified for this model. You should therefore first check whether your current battery configuration is suitable.

What should I do if my stock has a bit of play in it?

A small amount of play may occur due to differences in manufacturing tolerances between the stock and the tube. First, check that you are actually using a compatible combination. A stock that is too loose is not necessarily a faulty stock tube; it may simply be a difference in size.

Can I fit the stock tube myself?

This is possible if you are familiar with the construction of an M4 AEG. The exact procedure varies depending on the replica. Check beforehand how the existing tube is attached and take care not to damage any wiring during assembly. If in doubt, it is advisable to have the assembly carried out by an airsoft technician.

Advice from Airsoft-Legends

The 5KU 5-Position Stock Tube for M4 AEG is a practical choice if you want to replace the existing buffer tube on your M4 AEG or fit an adjustable stock as part of a custom build.

The combination of a metal construction, five adjustment positions and a length of 165 mm makes this a functional component for an M4 AEG configuration. The included mounting screw and shim are a useful addition.

Our most important advice is to check compatibility thoroughly beforehand. With stock tubes, it’s not just a question of whether a part is intended for an M4. How it attaches to the replica and the fit of the chosen stock are just as important.

If you’re looking for a metal 5-position buffer tube for a compatible M4 AEG, the 5KU-77 offers a simple and practical solution for replacing or modifying your stock assembly.