2019/01/05 Updated
Hello everyone (´-` )/
There are many conversion kits of HK416 PTW. For example, HAO and nborde develop the kits for PTW markets. Of course, these are very high quality but unfortunately, I am not rich man so these conversion kits are expensive for me. That means there no choice without making a converted HK416 upper receiver.
Fortunately, I can afford VFC and WE genuine receiver parts for HK416 GBB rifles in Japan. I had tried modifying them and succeeded ;) The modification is relatively easy for me.
■Required Tools■
Each examples are in parentheses as references. The milling machine can be substituted by the leutor or files
- Drill (SHINKO ACD-280)
- Grindstone with shaft φ
- Extension shaft for drill
- Flex hone (YANASE KENDAMA KTM-29-SC-60)
- Leutor (DREMELL 4000)
- Sanding band
- High speed cutter φ3
- Milling machine (PROXXON No. 27000)
- End mill φ6
■Step1: Expanding inside diameter of the receiver
The most important step is expanding inside diameter of the receiver for PTW cylinders. The VFC HK416 GBB receivers are made by aluminium die casting. That means the upper receiver has rough shape and diameter. In addition the diameter about φ24.5 at minimum that means it is too small for the PTW cylinder assembles.
At first, I tried rough machining by the grindstone with shaft which was extended by the extending shaft which was attached into the electric drill. This machining was very rough removal process which was conducted in a bucket which was filled up water. A good reasons for using water are cooling grindstones and prevention of scattering of cutting powder. In the process, only some specific places will be removed but that means succeeded. Because, the first process expand some specific places which are particularly small inner diameter.
Secondly, I switched the grindstone into the flex hone and grinded whole inner shape of the upper receiver as shown in Fig.1.
■Step2: Additional Expanding inner diameter for stepped inner diameter shape for PTW cylinders
SYSTEMA and other clone type cylinders have stepped outer shape as shown in Fig.2. That means you have to expand inner shape of the receiver more 0.5mm as diameter.
I used the leutor with the sanding band to expanding the inner diameter. The process is grinding a recess shape therefore, you can use rough machining tool.
If you have FCC type smooth outer shape cylinder, you can skip this process.
■Step3: Adding locating notch for a PTW cylinder
TW type upper receivers have a locating notch at a takedown pin block to hold the cylinder position. The notch has 4.5mm width and 10mm depth. You might think that "That is difficult process to add the notch!" but it isn't. Don't worry.
I used the leutor with the high speed cutter ∮3.0 for this process. At first, I milled rough shape notch on almost center of the takedown pin block. Positioning was just checking by my eyes. Then, I expanded the notch width to 4.5mm and digged to 10mm depth. If you miss notch position, you can revise the notch position until this expanding process.
The result as shown in FIg.3
■Step4: Cutting ribs for avoiding collision with magazines
Please wait a bit for the latest information;)
The most important step is expanding inside diameter of the receiver for PTW cylinders. The VFC HK416 GBB receivers are made by aluminium die casting. That means the upper receiver has rough shape and diameter. In addition the diameter about φ24.5 at minimum that means it is too small for the PTW cylinder assembles.
At first, I tried rough machining by the grindstone with shaft which was extended by the extending shaft which was attached into the electric drill. This machining was very rough removal process which was conducted in a bucket which was filled up water. A good reasons for using water are cooling grindstones and prevention of scattering of cutting powder. In the process, only some specific places will be removed but that means succeeded. Because, the first process expand some specific places which are particularly small inner diameter.
Secondly, I switched the grindstone into the flex hone and grinded whole inner shape of the upper receiver as shown in Fig.1.
 |
| Fig.1 The upper receiver after expanding inner diameter. |
■Step2: Additional Expanding inner diameter for stepped inner diameter shape for PTW cylinders
SYSTEMA and other clone type cylinders have stepped outer shape as shown in Fig.2. That means you have to expand inner shape of the receiver more 0.5mm as diameter.
I used the leutor with the sanding band to expanding the inner diameter. The process is grinding a recess shape therefore, you can use rough machining tool.
If you have FCC type smooth outer shape cylinder, you can skip this process.
 |
| Fig.2 Spring gude side outer shape of SYSTEMA PTW cylinder |
■Step3: Adding locating notch for a PTW cylinder
TW type upper receivers have a locating notch at a takedown pin block to hold the cylinder position. The notch has 4.5mm width and 10mm depth. You might think that "That is difficult process to add the notch!" but it isn't. Don't worry.
I used the leutor with the high speed cutter ∮3.0 for this process. At first, I milled rough shape notch on almost center of the takedown pin block. Positioning was just checking by my eyes. Then, I expanded the notch width to 4.5mm and digged to 10mm depth. If you miss notch position, you can revise the notch position until this expanding process.
The result as shown in FIg.3
 |
| Fig.3 The result of adding the locating notch for a PTW cylinder |
Please wait a bit for the latest information;)
