Project of retractable stock suitable for VFC G3A3 GBBR

■Background

 The VFC G3 GBBR is nice quality airsoft rifle but it has few optional aftermarket parts for customization. Especially, stocks and grips!
I found extremely cool design rifle stock is Spuhr R-410 but I can not import that into japan because ITAR regulation.
So, I determine that design similar retractable rifle stock for the VFC G3 GBBR.

How to convert VFC M4 bolt carriers suitable for WA M4 GBBRs

■Background■

 Recently, I fascinated WA GBBRs. An unique advantage of WA GBBRs is variation of outer aftermarket parts. However many aftermarket parts are discontinued especially, internal parts. So I have to find out alternatives.

■Required Tools and chemicals■

 Special tool or chemicals I used as follows. I think that the milling machine can be substituted by a leutor or files but I recommend using a milling machine.

1. Milling machine (ex: Proxxon No.27000 or better)
• ∮6.0 mill
2. Leutor (DREMELL 4000) 
• High speed cutter φ3
3. BIRCHWOOD Aluminum Black Metal Finish

■STEP1 Cutting down a valve locking notch■

Note: Especially, dimension of VFC bolt carrier is same as same real AR rifle bolt carrier. that means you have to use "real size" receiver or cut out back side of the VFC bolt carrier for the converting.

 Major difference between VFC genuine bolt carrier and WA's one is valve locking notch. The WA bolt carrier has a notch on bottom of the bolt carrier but VFC one does not have the notch as shown in Fig.1.

Fig.1 difference between WA type bolt carrier and VFC type one

 Dimension of the notch is shown in FIg.2. There are two slopes in front and back side of the notch. However, I believe that important dimension is length of flat surface. Because, a role of the slopes is realization of smooth moving of the valve control linkages on magazines. 
 I milled flat the flat surface by my little milling machine then, I added the slopes by the Leutor.  The result is shown in Fig.3. 

Fig.2 Dimension of the valve locking notch

Fig.3 Added the valve locking notch on the VFC bolt carrier

  After finishing modifying shape of the bolt carrier, you have to do firing test of your rifle with the converted bolt carrier. In my experience, I had to do some additonal modifying as follow sections.

■STEP2 Adding chamfer on a edge of a lock part■

 In current case, the VFC bolt carrier collision with a bolt catch. That means my rifle with the converted bolt carrier holds open after every shot even driven by full loaded magazine.  This process is not necessarily required for the converting of the VFC bolt carriers. I believe that this problem ocurred by some part dimensions of a firing pin block.
  Therefore, you have to check necessity of this process using your rifle with the modified bolt carrier after STEP1.

Fig.4 The lock part with chamfer (red circle) in front of the bolt carrier

■STEP3 Expanging inner diammetor of a  bolt carrier key■

 Usually, WA type GBB rifles have slightly shorter gas tube than real one. Thus, the WA blot carrier have bolt carrier key without hole which connects to the gas tube. the VFC bolt carrier has a bolt carrier key with slight small and shallow hole as shown in Fig.5.

Fig.5 The bolt carrier key on the VFC bolt carrier

 My rifle has longer gas tube (Fig .6) than WA genuine one. Even the VFC bolt carrier key collisions with the gas tube. That means more large and deep hole of the bolt carrier key is needed.
　

Fig.6  Longer gastube than WA genuine one which installed in my GBB rifle

 A solution is easy. That is just drilling! I used ∮4.8 drill and digged roughly 20mm depth as shown in Fig.7. As the result is shown in Fig.8. However if you adopt a "more realistic" gastube,  you have to expand the hole further more.

Fig.7 Drilling the bolt carrier key with a ∮4.8 drill

Fig.8 The modifyed bolt carrier key

■Conclusion■
 Finally, I finished converting the VFC M4 bolt carrier suitable for WA rifles. I satisfied the result because the converted bolt carrier works perfectly. 

Review of the ARES High Torque Slim AK AEG Motor

■BACKGROUND
 I have an AK104 AEG manufactured by E&L but the rifle had been left long time.  Recently, I found a nice motor which manufactured by ARES airsoft. So I purchased and tried that.
 Many Tokyo Marui and clone AEGs have more thicker grip to contain a motor than real models . Couple years ago, new slim motors and grips for M4s and AKs were released by ARES airsoft.
 I purchased The ARES High Torque Slim AK AEG Motor includes a dedicated grip(PG-M-002-BK).  As another option, ARES has a super high torque version but unfortunately, the super high torque version was not available at a store in near my home.

Fig.1 As an example: the slim motor on Redwolf airsoft

Fig. 2 The built-in ARES slim motor into the AK gearbox. The motor fixed by two screws (orange arrows)

■REVIEW OF THE ARES SLIM MOTOR
 I think that installation is easy for airsofters who can disassemble and assemble gearboxes. After detaching a grip, replacing  a old motor with the new slim motor which fixed by two screws (Fig.2). In Fig.2, The motor housing seems work as mechanical frame to support mechanical stress from gripping or gun handling. That concept is similar to motors for PTWs as shown Fig.3.  The PTW motor is fixed rigidly the motor base into the lower receiver by spring pins.

  However, the ARES slim motor unit has gap between the motor housing and the motor mount plate to adjust bevel gear position as Fig.4 . Construction of the mechanism is Fig.5(Left pic). The gap is made from screw between the motor base and the motor housing. The gap makes mechanical rattling not only the motor housing but also the axis and the bevel gear. I think that the mechanical rattling make wearing of the bevel gear, a bearing on the motor housing and the screw of the motor housing but that will be long time scale. it is not critical problem in usual condition use.

Fig.3 An example of the PTW motor

Fig. 4 Adjusting bevel gear position. This figure means bevel gear position is adjustable  only every 180deg 

Fig. 5 Mechanical structure of the ARES slim motor (Left pic) and incline mechanism of the motor housing (Right pic)

  Because, the dedicated grip should be main pillar to support mechanical strain but that achieved by suitable fitting to receiver. For appropriate fitting into the E&L AK104, some additional shaving down are needed as Fig. 6. Firstly, as the left picture of Fig. 6, I had expanded the notch which fit to a trigger guard. Secondly, as the right picture of Fig. 6, I had cut the convex shape to fit the receiver side notch. You can shave down the grip by files but I recommend using a micro grinder.

Fig. 6 the shaved down grip

 As another tip, inserting shims (I used M4 washers which are 0.8mm thickness as shown Fig. 7) between the end bell and the grip bring tight or not of the grip end screws very clearly.

Fig, 7 Shims on the end bell of the slim motor

 Amazingly the ARES slim motor and the grip make dramatic difference.  Dimension of the slim grip is similar to real AK grips. Exterior of the grip after replacement is Fig.8. The ARES AK grip is extremely thinner than a genuine SAW type grip as shown Fig.9.
 Unfortunately, there are no third party or different shape grips as far as I know. Perhaps, we can convert real AK grips for the ARES slim motor but it could be difficult process.

Fig. 8 The fitted slim grip on the AK104

Fig. 9 Comparison of the ARES grip and the genuine SAW type grip

 About performance of the ARES slim motor, I think that is average but I can not conclude about performance by specific values because I have no measurement instruments. I feel that the ARES slim motor has enough performance to drive around M100 springs. Perhaps, it is better idea that using super high torque version to drive M120 or more strong spring.

■CONCLUSION
 The slim motor is a nice choice for airsofters who don't like too thick grips of AEGs.  Also, It has enough performance for under 0.989J regulation in Japan. However, I guess the slim motor has lower mechanical strength than common type motor housing for V3 gearboxes. Perhaps, the structure of the slim motor makes relatively short mechanical lifetime.  In addition, currently there are no other shape grips for customising.
 Certainly, the ARES slim motor has some drawbacks but even considering about it, the ARES slim motor is best solution if you want realistic size grip for AK AEGs.

HK417 PTW Project/Magazine modification

In this page, instructions of a magazine modification for the PTW HK417 are explained.

■OVERVIEW■
 After transplanting the PTW system into the VFC HK417, you can not use VFC GBB magazines.  In this page, diversion of the magazines of the Tokyo Marui HK417 AEG is instructed.

■STEP1: VERIFYING MAGAZINE PROBLEM OF THE PTW HK417■
 SYSTEMA PTW is AEG system so if you transplant the PTW system into GBB rifles, you can not use anymore magazines of these GBBs.  Therefore, you have to find out a substitution.  In this project, I used magazines of  the Tokyo marui HK417 AEG as the substitution.

 Some readers may say "VFC makes the AEG version HK 417. Why do not you use that magazine?"
  The good reason is an empty detection system of the PTW AEG system.  SYSTEMA PTWs and Tokyo Marui next gen AEGs detect empty of magazines.  However,  the VFC AEG version HK417 dose not have that feature. That means it is easy for you to use magazines of Tokyo Marui HK417 as substitution for the PTW HK417 magazines.

Fig.1 the VFC HK417 GBB magazine and the Tokyo Marui HK417 AEG magazine

■STEP2: VERIFYING DIFFERENCES BETWEEN VFC & TOKYO MARUI MAGAZINES■

  In this project, I divert AEG HK417 magazines made by  Tokyo Marui for PTW HK417.  Fortunately,  I could convert Tokyo Marui magazines for the PTW HK417 easily.  There is 1[mm]  difference of longitudinal length between VFC magazines and Tokyo Marui one as shown Fig.2.  The difference produces very tight and difficult insertion of magazines for operators.  

Fig. 2 Dimension difference between the VFC and Tokyo marui magazine

■STEP3: ADDITIONAL PROCESSING OF TOKYO MARUI MAGAZINES■
  For converting the magazines made by Tokyo Marui for the PTW HK417, you have to shave fore and back end side 0.5[mm] each.  Shaving area is shown as Fig.3.  That figure means you do not have to shave an rib surface of the  back side of magazines because, VFC and Tokyo Marui magazines have same maximum longitudinal length.
 After shaving, the magazines must be as shown Fig.4.  I had used an ultra-micro milling machine for shaving front side, and a micro grinder for shaving back side. However, you can shave that with files.

Fig.3 Shaving area of the Tokyo Marui magazine

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How to convert the VFC HK416 GBB upper receiver to suitable for the PTW

2018/05/23 First version
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

1. Drill (SHINKO ACD-280)
1. Grindstone with shaft φ
2. Extension shaft for drill
3. Flex hone (YANASE KENDAMA KTM-29-SC-60)
2. Leutor (DREMELL 4000)
1. Sanding band
2. High speed cutter φ3
3. Milling machine (PROXXON No. 27000)
1. 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.

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

■Step4: Cutting ribs for avoiding collision with magazines
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HK417 PTW Project/Motor modification

In this page, instructions of the PTW motor modification to fit to PTW HK417 is explained.

■OVERVIEW■
 Lower receivers of the PTW M4s have mechanical structure for fixing a PTW motor. However, of course, the VFC HK417 GBB dose not have one.  Therefore, you have to design and make a motor mounter for the PTW motor fixing into the VFC HK417 GBB lower receiver.

■STEP1: VERIFYING PROBLEMS TO FITTING THE PTW MOTOR INTO THE VFC HK417 GBB■
 Lower receivers of the PTW M4s have mechanical structure for fixing a PTW motor like as Fig.1. However, the lower receiver of the VFC HK417 GBB dose not have one.  Real AR rifles and M4 GBB rifles have a grip mounter in this spot, so you think like that "Is solution additional machining of holes and a slot?". Unfortunately, it is not (; 'A`)

 

Fig.1 Mechanical structure of  the PTW M4 for fixing the PTW motor

  A critical problem is that the lower receiver of the VFC HK417 GBB has an detachable grip mounter as shown  Fig. 2.  This grip mounter has three screw holes. One hole is used for fixing a grip. Other two screw holes are used for fixing itself into the lower receiver of the VFC HK417 GBB. Latter two screw holes interfere in spring pin holes fixing the PTW motor.  That means it is inappropriate for the lower receiver of the VFC HK417 GBB to additional machining.
  A solution of this project is modifying the PTW motor base. That means developing a new motor base integrates the PTW motor base and the grip mounter of the VFC HK417 GBB.

Fig.2 The Grip mounter of the VFC HK417 GBB

■STEP2: DESIGNING THE MOTOR BASE■
 As the solution of the problem, I had designed a new motor base as shown Fig.3

Fig.3 The new motor base for HK417 PTW

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HK417 PTW Project

Hello everyone (´-` )/

This is a front page of  HK417 PTW Project.
I will add more information sequentially.

■PURPOSE■

 The purpose of this project is transplanting the PTW system into the VFC/UMAREX HK417 GBBR.  This page will include some instructions of design and modifying for converting in near future, but now this page is under construction.

■MOTIVATION■

 The Professional training weapon (PTW) is one kind of airsoft guns driven by an electric motor designed and developed by SYSTEMA. The design of PTW is clever and delicate. However, Sadly, SYSTEMA's PTW lineup is just M4 carbine and MP5 sub-machine gun despite of a very compact gear case unit. Of course, especially on the M4 carbine, you can assemble and enjoy many types of setups however, these cores are still the M4 carbine.  The motivation of this project is that it is pretty cool for me  to use a gun that is very different from other airsofters.

■DESIGN AND METHOD■

 More modifications and new part design are required for the transplanting than your expectation.  At first, for putting the PTW gearcase, milling a lower-reciever not only but also modifying a motor, a sun-gear and an electric circuit are needed.
Secondly, making a sleeve and an extension for the PTW cylinder are needed because the cylinder has to be larger size to insert properly into the HK417 upper-receiver. That means you have to spend labour more than your assumption to the converting.

 Detailed information will be added sequentially.

1. Milling lower receiver
2. Motor modification
3. Magazine modification
4. Gearcase modification and gear design
5. ECU modification
6. Design for cylinder assembly adaptor
7. Design for outer barrel adaptor