KWA 2GX Mech-box w/ 9mm Bearings
Feb 25, 2011 14:21:30 GMT -5
Post by triggs (SABR) on Feb 25, 2011 14:21:30 GMT -5
Full Album Review – KWA 2GX 9mm Gearbox
KWA 2GX Mech Box with 9mm Bearings
- Overview
- Accessories
- Externals review
- Internals review
- Performance
- Final Thoughts and Upgradeability
Overview
In mid 2009 KWA USA (www.kwausa.com) announced they would be releasing an updated version of their M4 series with the age old Version 2 (v2) gearbox. Like most v2 gearboxes the original KWA gearboxes were known to crack under stress from the piston slamming into the cylinder and the shock being absorbed by the front part of the shell, despite being “engineered to outperform.” The answer to this was the 2GX (second generation) shell. In 2010 KWA USA finally released the 2GX shell as a barebone part, available to purchase separately from their M4 series.
Accessories
As far as accessories go, the KWA 2GX shell is pretty sparse. Mine came wrapped in a thin shrink wrap with the KWA logo and information printed on a sticky label. The only included accessories included are six 9mm bearings.
Externals Review
Externals are pretty simple. Outer dimensions are virtually identical to a standard version Classic Army as seen in the pictures.
Starting from the back it’s identical to any v2 gearbox.
The middle is where it starts to change. As seen the KWA features a flat section instead of a curved portion behind the piston like that on the Classic Army (CA) shell. The KWA AEG’s flip open like a real M4, though the flattened portions may simply be for looks rather than function.
The front however, is fundamentally different. As noted earlier the original KWA shells were prone to breaking at the front. This is a common problem even with the original Tokyo Marui (TM) v2 shells. It’s simply a design flaw in the shell, although TM’s aren’t known for cracking due to the low FPS they generally use. Standard v2 gearboxes like the CA however, can usually only withstand 400FPS or so. However, for the number of applications of the v2 in rifles such as the MP5, G3, M4/M16, and many others, the weak gearbox is a problem, especially for the high ROF or high FPS crowds. KWA has answered this problem by completely redesigning the front end. It’s obvious that the front end has been highly reinforced in the area most prone to cracking. Many reports since the release of the 2GX series have been praising the design for withstanding at least an M150 spring.
The only last external note is the 9mm bearings. This is probably the only flaw in the design. A large number of 2GX rifles, with the exception of the KWA SR7 CQB M4, are known for shooting an extremely high 410-450FPS out of the box. The shell itself may be able to withstand the stress, unfortunately the bearings are not, with a large number of complaints and reports of the bearings exploding inside the gearbox and sending shrapnel into the gears and piston. You may have noticed that a few pictures feature a new set of solid metal bushings. The gearbox build that was taking place during the picture taking got a little confusing so there may be some noticeable changes.
Internals Review
Internally is where the KWA 2GX gets a bit tricky. The back is not reinforced like typically marketed “reinforced” gearboxes. This is neither a pro or con, as this is never a weak area so the normal reinforced gearboxes waste metal and add unneeded weight. KWA has avoided this, leaving a large open space.
The first area of concern is the base of the shell where the spring guide sits. The KWA spring guides appear to have much longer “fins” that lock into the shell’s body. A standard guide fits into the milled cutouts (seen on the right) just fine (seen on the left) however the tab (seen on the right of the spring guide) do not sit all the way in like on a normal shell. This doesn’t appear to affect performance but it is a strange and possibly troublesome area later on. Guarder spring guides fit (loosely) due to a tab designed “fin”, however Classic Army and other companies with rod style “fins” will not fit.
The next set of problems is in the trigger area. The first noticeable difference is the reinforced trigger trolley stop, which is twice as thick as normal on the 2GX shell. For a normal gear set this won’t be a problem, however, if building a high FPS setup, a set of Infinite Torque Up (ITU) gears like those shown in the picture will interfere with the post and require modification.
The third problem with the trigger area is the distance between the physical trigger and the trigger trolley (the part that actually touches the contacts making an electrical circuit) are slightly different dimensions in comparison to standard AEG’s. This means without special modifications (as seen in the pictures) a standard trigger contact set will not work.
The fourth area of concern is the cylinder head lugs that hold the cylinder head in place are slightly larger than normal and certain aftermarket parts (such as the Guarder I tested with) might require slight modification to fit.
The last area of study is the screw holes themselves. As seen in the first picture, the shell does not include any screws to hold the shells together. After a quick trip to the hardware store it became obvious the shell had one other little secret. The screw holes are left untapped. i.e. they are not threaded for any screws. This is in a way a nice thing as it allows a couple choices in screws, British or Metric style screws can be used after using a proper sized tap. I chose the universal standard gearbox 3mm with a .5 pitch.
Performance
As stated earlier there are a number of reports of the KWA 2GX shell withstanding a M150 spring ~490FPS~ even in full automatic. As of now, the initial testing seems to prove this in the test build centered around a Guarder SP150 (the Guarder equivalent to a SystemA M150).
Further testing will be required, but it appears this might be one of the few shells that can handle high FPS without failure.
Editor’s note 2017: After 5 years of use and countless rounds cycled, the gearbox shows no signs of fatigue or cracking. I am very pleased with this shell for my Semi-Auto build.
Final Thoughts and Upgradeability
For many years the only options for high FPS setups were the Haynes and ProWin milled aluminum gearboxes. These have long since been out of production however, and when available are extremely expensive. In recent years there have been a number of cheaper aluminum gearboxes, but their quality is unknown. The KWA 2GX mech box is a cast design so it is uncertain if it can compete with the stronger milled gearboxes, but the first year or so of reports seem promising.
With a number of modifications the 2GX seems to offer a “cheap” alternative.
Externals Score: 7/10
Externally the 2GX is flawless, however the exploding bearings is a serious issue for upgraders
Internals Score: 8/10
Internally I have to knock of a few points due to the number of non-standard specs in the trigger, spring guide, and cylinder head areas.
Overall score: 8/10
Unless you are a serious builder with intimate knowledge of gearboxes and tools the 2GX gearbox will be a headache to build from scratch. KWA does however offer a complete drop in gearbox through their online shop.
It also should note that due to the design of the reinforcements it CANNOT BE GUARANTEED that the KWA 2GX gearbox will fit in anything EXCEPT the KWA 2GX bodies. It is highly suggested that careful consideration be taken when examining the clearances between the upper receiver and lower receiver.
© Copyright triggs 2017
KWA 2GX Mech Box with 9mm Bearings
- Overview
- Accessories
- Externals review
- Internals review
- Performance
- Final Thoughts and Upgradeability
Overview
In mid 2009 KWA USA (www.kwausa.com) announced they would be releasing an updated version of their M4 series with the age old Version 2 (v2) gearbox. Like most v2 gearboxes the original KWA gearboxes were known to crack under stress from the piston slamming into the cylinder and the shock being absorbed by the front part of the shell, despite being “engineered to outperform.” The answer to this was the 2GX (second generation) shell. In 2010 KWA USA finally released the 2GX shell as a barebone part, available to purchase separately from their M4 series.
Accessories
As far as accessories go, the KWA 2GX shell is pretty sparse. Mine came wrapped in a thin shrink wrap with the KWA logo and information printed on a sticky label. The only included accessories included are six 9mm bearings.
Externals Review
Externals are pretty simple. Outer dimensions are virtually identical to a standard version Classic Army as seen in the pictures.
Starting from the back it’s identical to any v2 gearbox.
The middle is where it starts to change. As seen the KWA features a flat section instead of a curved portion behind the piston like that on the Classic Army (CA) shell. The KWA AEG’s flip open like a real M4, though the flattened portions may simply be for looks rather than function.
The front however, is fundamentally different. As noted earlier the original KWA shells were prone to breaking at the front. This is a common problem even with the original Tokyo Marui (TM) v2 shells. It’s simply a design flaw in the shell, although TM’s aren’t known for cracking due to the low FPS they generally use. Standard v2 gearboxes like the CA however, can usually only withstand 400FPS or so. However, for the number of applications of the v2 in rifles such as the MP5, G3, M4/M16, and many others, the weak gearbox is a problem, especially for the high ROF or high FPS crowds. KWA has answered this problem by completely redesigning the front end. It’s obvious that the front end has been highly reinforced in the area most prone to cracking. Many reports since the release of the 2GX series have been praising the design for withstanding at least an M150 spring.
The only last external note is the 9mm bearings. This is probably the only flaw in the design. A large number of 2GX rifles, with the exception of the KWA SR7 CQB M4, are known for shooting an extremely high 410-450FPS out of the box. The shell itself may be able to withstand the stress, unfortunately the bearings are not, with a large number of complaints and reports of the bearings exploding inside the gearbox and sending shrapnel into the gears and piston. You may have noticed that a few pictures feature a new set of solid metal bushings. The gearbox build that was taking place during the picture taking got a little confusing so there may be some noticeable changes.
Internals Review
Internally is where the KWA 2GX gets a bit tricky. The back is not reinforced like typically marketed “reinforced” gearboxes. This is neither a pro or con, as this is never a weak area so the normal reinforced gearboxes waste metal and add unneeded weight. KWA has avoided this, leaving a large open space.
The first area of concern is the base of the shell where the spring guide sits. The KWA spring guides appear to have much longer “fins” that lock into the shell’s body. A standard guide fits into the milled cutouts (seen on the right) just fine (seen on the left) however the tab (seen on the right of the spring guide) do not sit all the way in like on a normal shell. This doesn’t appear to affect performance but it is a strange and possibly troublesome area later on. Guarder spring guides fit (loosely) due to a tab designed “fin”, however Classic Army and other companies with rod style “fins” will not fit.
The next set of problems is in the trigger area. The first noticeable difference is the reinforced trigger trolley stop, which is twice as thick as normal on the 2GX shell. For a normal gear set this won’t be a problem, however, if building a high FPS setup, a set of Infinite Torque Up (ITU) gears like those shown in the picture will interfere with the post and require modification.
The third problem with the trigger area is the distance between the physical trigger and the trigger trolley (the part that actually touches the contacts making an electrical circuit) are slightly different dimensions in comparison to standard AEG’s. This means without special modifications (as seen in the pictures) a standard trigger contact set will not work.
The fourth area of concern is the cylinder head lugs that hold the cylinder head in place are slightly larger than normal and certain aftermarket parts (such as the Guarder I tested with) might require slight modification to fit.
The last area of study is the screw holes themselves. As seen in the first picture, the shell does not include any screws to hold the shells together. After a quick trip to the hardware store it became obvious the shell had one other little secret. The screw holes are left untapped. i.e. they are not threaded for any screws. This is in a way a nice thing as it allows a couple choices in screws, British or Metric style screws can be used after using a proper sized tap. I chose the universal standard gearbox 3mm with a .5 pitch.
Performance
As stated earlier there are a number of reports of the KWA 2GX shell withstanding a M150 spring ~490FPS~ even in full automatic. As of now, the initial testing seems to prove this in the test build centered around a Guarder SP150 (the Guarder equivalent to a SystemA M150).
Further testing will be required, but it appears this might be one of the few shells that can handle high FPS without failure.
Editor’s note 2017: After 5 years of use and countless rounds cycled, the gearbox shows no signs of fatigue or cracking. I am very pleased with this shell for my Semi-Auto build.
Final Thoughts and Upgradeability
For many years the only options for high FPS setups were the Haynes and ProWin milled aluminum gearboxes. These have long since been out of production however, and when available are extremely expensive. In recent years there have been a number of cheaper aluminum gearboxes, but their quality is unknown. The KWA 2GX mech box is a cast design so it is uncertain if it can compete with the stronger milled gearboxes, but the first year or so of reports seem promising.
With a number of modifications the 2GX seems to offer a “cheap” alternative.
Externals Score: 7/10
Externally the 2GX is flawless, however the exploding bearings is a serious issue for upgraders
Internals Score: 8/10
Internally I have to knock of a few points due to the number of non-standard specs in the trigger, spring guide, and cylinder head areas.
Overall score: 8/10
Unless you are a serious builder with intimate knowledge of gearboxes and tools the 2GX gearbox will be a headache to build from scratch. KWA does however offer a complete drop in gearbox through their online shop.
It also should note that due to the design of the reinforcements it CANNOT BE GUARANTEED that the KWA 2GX gearbox will fit in anything EXCEPT the KWA 2GX bodies. It is highly suggested that careful consideration be taken when examining the clearances between the upper receiver and lower receiver.
© Copyright triggs 2017