Guides and Tutorials

UPGRADE GUIDE | ACCURACY

| 3. ACCURACY |

| 3. ACCURACY |

AEG, Bolt Action, GBB or HPA, every system relies on a hop up rubber to provide the back spin to our BB's. Hop Up Rubbers (or Buckings) come in varying degrees of rubber hardness, with different lip designs and contact patches / mounds, all adding their own pros and cons. Although the stock up up rubber performs very well, upgrading to an aftermarket rubber can make drastic changes to the consistency and stability of each shot, and therefore your MK23's accuracy.

What does it do?
The Hop Rubber in your MK23 has a large part in determining how much backspin is applied to the BB as it passes through and in to the barrel. Most hop up rubbers that you will interact with feature a uniquely designed mound at the top of the rubber that is pressed down in to the path of the BB so that it contacts the top side of the BB and imparts additional backspin to the BB. The shape and placement of the mound (or contact patch) can have a drastic effect on how the BB behaves as it leaves the barrel.

For example a long and concave curve shaped mound can apply backspin to the top and sides of the BB for a prolonged period of time before entering the barrel, resulting in extended and more controlled BB flight (Range and Accuracy). Conversely, a poorly shaped or damaged mound can result in performance loss, with the BB curving off at unwanted directions or falling short of expected engagement ranges.

In addition to the mound designs, hop rubbers can also come in varying degrees of hardness and textures. For example, softer rubbers can perform better in colder temperatures and lower FPS output weapons like the MK23, whilst harder rubbers are more durable and are more capable of effecting heavier weight BB's in warmer temperatures. The benefits of the different rubber textures and hardness are usually outlined by the hop up rubber manufacturer.

Why do you need it?
If you are looking to obtain more stable BB flight, adding an aftermarket hop up rubber to your stock or upgraded inner barrel is one of the easiest and relatively low cost upgrades you can perform. A new hop up bucking can have game changing results, allowing you to gain more shot to shot consistency and therefore accuracy. Your confidence in your shots behaving the same way with each shot will allow you to approach contact scenarios with less hesitation.

As a word of caution however, making changes to how your current MK23s hop up performs by replacing the hop up rubber may require some fine adjustment and use before you see noticeable improvements. Be prepared to re-learn how your weapon behaves, but do not be hesitant to try this upgrade, it's usually completely worth it.


How do I modify/install it?
The MK23 only accepts VSR-10 compatible inner barrels and hop up rubbers. When considering a rubber in your MK23, ensure that the rubber is compatible with the shape of the inner barrel window used (Open or non-bridged window type only). Please bare in mind that if you are using other modifications in your MK23 that may effect the hop up rubber (such as the TDC mod), be sure to correctly install them for use with the bucking to ensure accurate BB flight and intended function of the hop up rubbers design. 

You can replace the hop up rubber installed in your MK23 by following these steps:

  1. Remove the slide from the body.

  2. Remove the hop assembly/barrel unit from the slide.

  3. Remove the dust cover from the assembly, removing the spring beneath the dust cover at the same time.

  4. Remove the center screw / pin from the outer barrel.

  5. Slide off the outer barrel from the assembly.

  6. Remove the two assembly body screws.

  7. Separate the two assembly body halves with the barrel kept in place and laid flat and exposed on a surface.

  8. Remove the hop arm from the assembly.

  9. Remove the inner barrel with the hop rubber attached.

  10. Remove the old hop rubber from the barrel.

  11. Replace the old hop rubber with the new hop up rubber, ensuring that the rubber fits securely to the grooves of the barrel and that there is no bulging present.

  12. Apply the "Teflon Seal" Mod (see below in this guide).

  13. Return the barrel and hop rubber to their slots in the hop up assembly, and ensure that the rubber and barrel fit snugly.

  14. Return the hop arm to the assembly.

  15. Return the two assembly body halves together.

  16. Return the two assembly body screws.

  17. Return the outer barrel to the assembly.

  18. Return the center screw / pin to the outer barrel.

  19. Return the dust cover spring and dust cover.

  20. Return the hop assembly to the slide.

  21. Return the slide to the body.

This mod is applicable for all MK23 models.

PART: Inner Barrel

Like the hop rubber, the standard barrel in the MK23 (Tokyo Marui) is by no means bad and will perform admirably for as long as you keep it in the gun. However, aftermarket barrels of higher quality can certainly bring with them the desirable qualities that you are looking for when upgrading, such as tighter shot groupings, better range and increased FPS - all of which equate to improved accuracy. There are some key factors that must be considered when upgrading a MK23 barrel, these are: Barrel Length, Bore Diameter, Window Type and Notch placement. 

Barrel Length:
- A barrel longer than 133mm will not be able to pass through the slot in the outer barrel of the MK23.

- A barrel longer than 150mm will exceed the flash hider of the outer barrel and be visible.

- A barrel longer than 150mm will exceed 350FPS on 0.20g BB's.

- A barrel longer than 220mm will exceed 400FPS on 0.20g BB's

- A barrel of 310mm will reach 420/430 FPS.

- A barrel longer than 310mm may start to decrease in FPS down from 430 FPS.

 

Bore Diameter:

- The stock bore diameter is 6.08.

- The tighter (smaller) the bore, the higher the exit FPS of the barrel. This is due to how gas is compressed.

Window Type:

The window, or area closest to the nozzle where the hop up rubber mound makes contact with the BB can be of two types. Either Closed/Bridged or Open/Unabridged. In the MK23, you only want to use an Open type due to how MK23 compatible barrels are designed.

Notch placement:

The stock barrel has a small notch designed in it right next to where the hop rubber seats when fit on to the barrel. This notch is used to help secure the inner barrel to the hop up assembly where a small nub locks in to the notch in the barrel. On some aftermarket barrels, the placement of the notch is positioned slightly further down on the inner barrel, meaning that it does not align and lock in to the nub in the hop up assembly. Users are required to file away the nub in the hop up assembly so that the inner barrel can seat flush in the hop up assembly or use an alternative inner barrel with the notch correctly placed on the barrel.



This mod won't detail the pro's and cons of tightbore vs widebore, brass versus stainless steel, or whether it features a unique bore design.

The purpose of this mod is to allow the user to modify the outer barrel so that an inner barrel longer than the stock length of 133mm can be used in their MK23, while considering the key factors outlined above.

 

What does it do?

The installation of an aftermarket inner barrel can provide the user with increased range, increased FPS and increased accuracy, all with additional opportunity to install a compatible aftermarket hop up rubber that can be used in conjunction with the inner barrel that will only increase all of these factors together.

The installation of a longer than standard length inner barrel requires that the user drill out a larger inner diameter for the outer barrel. This is to allow the longer length of the inner barrel to pass through the outer barrel. You will need a drill bit between 8.5mm and 9mm in size to accommodate the outer diameter of most aftermarket inner barrels.

Why do you need it?

Without performing this mod, it is simply not possible to install an aftermarket barrel in the MK23 that is longer than 135mm in length or 8mm in width. The outer barrel must be drilled out or filed out for the barrel to pass through it's center.


How do I modify/install it?

In short the Inner Barrel is installed by the following steps:

 

  1. Remove the slide from the body.

  2. Remove the hop assembly/barrel unit from the slide.

  3. Remove the dust cover from the assembly, removing the spring beneath the dust cover at the same time.

  4. Remove the center screw / pin from the outer barrel.

  5. Slide off the outer barrel from the assembly.

  6. Place the outer barrel in an upright position in a vice or another means of securing the outer barrel in preparation for the use of a drill.

  7. Using a 8.5mm to 9mm drill bit, slowly drill away material from the outer barrel with the drill bit positioned directly in the center of the outer barrel "bore".

  8. Continue to drill through the material until the drill bit passes through cleanly to the the other side of the outer barrel.

  9. Using the new inner barrel, ensure that the entire width of the inner barrel can pass through the out barrel smoothly.

  10. Clean up the outer barrel for any burrs or sharp edges.

  11. Place the outer barrel to one side and continue disassembly.

  12. Remove the two assembly body screws.

  13. Separate the two assembly body halves with the barrel kept in place and laid flat and exposed on a surface.

  14. Remove the hop arm from the assembly.

  15. Remove the inner barrel with the hop rubber attached.

  16. Remove the old hop rubber from the barrel.

  17. Replace the old inner barrel with the new inner barrel.

  18. Replace the old hop rubber with the new hop up rubber if available, ensuring that the rubber fits securely to the grooves of the new inner barrel and that there is no bulging present.

  19. Apply the "Teflon Seal" Mod (see below in this guide).

  20. Return the barrel and hop rubber to their slots in the hop up assembly, and ensure that the rubber and barrel fit snugly.

  21. Return the hop arm to the assembly.

  22. Return the two assembly body halves together.

  23. Return the two assembly body screws.

  24. Apply the "Inner Barrel Spacer" Mod to prevent any barrel wobble from potential tolerance issues after drilling.

  25. Return the outer barrel to the assembly.

  26. Return the center screw / pin to the outer barrel.

  27. Return the dust cover spring and dust cover.

  28. Return the hop assembly to the slide.

  29. Return the slide to the body.

MODIFICATION: Inner Barrel Spacer

Inner barrel spacers come in all shapes and sizes, as aftermarket parts or DIY modifications. Inner Barrel spacers are one of the most common modifications performed by users to increase inner barrel accuracy and prevent inner barrel wobble within the outer barrel during use. 

What does it do?
The Inner Barrel Spacer mod simply uses one or more o-rings (or several layers of electrical tape) to create a buffer around the inner barrel so that when it is inserted through the outer barrel, the spacer fills the empty space between the inner barrel and the outer barrel. This allows the inner barrel to hold a central position in the outer barrel and prevent any unwanted movement during use. You may need to try different sizes of o-rings or several layers of electrical tape to get a perfect fit around the inner barrel and within the outer barrel.

Why do you need it?
If you inspect the inside of the outer barrel and watch as you place the inner barrel within it, you will notice that the there is a considerable amount of space around the inner barrel. Although this extra space around the inner barrel is not a real concern when using a stock length inner barrel (133mm in length) or shorter as the front of the outer barrel narrows, after drilling out the front of the outer barrel to allow for a longer inner barrel (as seen in the Inner Barrel mod above); this extra room can result in unwanted movement due to tolerance issues after drilling.

This mod is also particularly helpful to carbine kit users with longer internal inner and outer barrels in order to prevent free-floating and unsupported barrels.


How do I modify/install it?
Adding the Inner Barrel Spacers is simple, use the following steps
:

 

  1. Remove the slide from the body.

  2. Remove the hop assembly / barrel unit from the slide.

  3. Remove the center screw / pin from the outer barrel.

  4. Slide off the outer barrel from the assembly.

  5. Using an o-ring with an inner diameter of at least 8mm (smaller when stretched may work equally well), slide the o-ring down the exposed inner barrel.

  6. Depending on the length of the inner and outer barrel, add additional o-rings at even intervals to the inner barrel to prevent movement.

  7. Replace the outer barrel by sliding it over the inner barrel and o-ring spacers (If the o-ring prevents this, try a smaller size).

  8. Replace the center screw / pin in to the outer barrel.

  9. Replace the hop assembly / barrel unit in to the slide.

  10. Replace the slide on to the body.

MODIFICATION: Teflon Seal

The Teflon Seal mod is a quick solution to ensuring an airtight barrel from the moment the BB enters the hop up bucking chamber to the point that exits the barrel.

What does it do?
The mod uses PTFE Teflon Thread / Plumbing tape to create a seal around the edge of the hop rubber where it meets the inner barrel (opposite side to the nozzle). By adding several layers of the PTFE tape around this joining point between the rubber and barrel, you are able to eliminate any tiny gaps and intolerance's where air/gas may escape from as it passes through the hop and in to the barrel.

Why do you need it?
Ensuring an airtight seal between the barrel and hop rubber is a critical step to having a consistent shot to shot FPS in your MK23. Adding the Teflon Seal to your barrel setup can result in a increase of as much as 10 - 20 FPS depending on the quality of the barrel and hop rubber used, but more importantly will improve shot accuracy due to the added consistency between each shot. For such a simple, cheap and effective modification, there is no reason not to add it to your "to do" list when next inside the gun.

How do I modify/install it?

In short the Teflon Seal is installed by the following steps:

 

  1. Remove the slide from the body.

  2. Remove the hop assembly/barrel unit from the slide.

  3. Remove the dust cover from the assembly, removing the spring beneath the dust cover at the same time.

  4. Remove the center screw / pin from the outer barrel.

  5. Slide off the outer barrel from the assembly.

  6. Remove the two assembly body screws.

  7. Separate the two assembly body halves with the barrel kept in place and laid flat and exposed on a surface.

  8. Remove the hop arm from the assembly.

  9. Remove the inner barrel with the hop rubber attached.

  10. Using the PTFE Tape, wrap 2 - 3 layers around the barrel under tension so that the the middle of the tape covers the edge of the hop rubber where the rubber meets the barrel (opposite side to where BB's enter the rubber), and that there is ample tape either side.

  11. Cut the tape and smooth down the surface of the tape on the joined area to ensure a tight fit.

  12. Return the barrel and hop rubber to their slots in the hop up assembly, and ensure that the rubber and barrel fit snugly. Smooth down the PTFE tape or remove a layer of the tape if you have fitment issues when returning the barrel to the assembly.

  13. Return the hop arm to the assembly.

  14. Return the two assembly body halves together.

  15. Return the two assembly body screws.

  16. Return the outer barrel to the assembly.

  17. Return the center screw / pin to the outer barrel.

  18. Return the dust cover spring and dust cover.

  19. Return the hop assembly to the slide.

  20. Return the slide to the body.

This mod is applicable for all MK23 models.

 
 
 
 

PART: Hop Up Rubber

 

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