AIM/TOP M120 Drop-in Gearbox
Aug 10, 2012 23:14:32 GMT -5
Post by triggs (SABR) on Aug 10, 2012 23:14:32 GMT -5
Full Album Review – AIM/TOP M120 Gearbox
AIM/TOP M120 “Super Reinforced” Complete Gearbox
- Overview
- Accessories
- Externals review
- Internals review
- Performance
- Final Thoughts and Upgradeability
Overview
As a custom airsoft gunsmith I’m usually against buying any pre-made gearboxes as they generally require more work than they’re worth. However, recently, individual products within the US have become harder, or more expensive, to find than a basic drop in gearbox. So I ended up picking up one of the AIM/TOP complete gearboxes for a custom built M4 for a customer.
Accessories
The AIM/TOP gearbox comes with literally no accessories. It comes in its box with good quality foam packing and that’s all.
I ordered a front wired gearbox as that was all the store had in stock at the time, and much to my surprise the box didn’t include the section of the wiring harness that includes the battery connector. If it wasn’t for the fact I was already planning on a custom wiring harness I would have easily been more annoyed.
Externals Review
Externally there’s very little to mention. While the box lists this as a “Super Reinforced” gearbox it’s clear from the outside there is no additional reinforcement compared to a standard Tokyo Marui gearbox, unlike the KWA 2GX shell I reviewed earlier.
The only thing distinguishing this gearbox from a JG/clone gearbox is the AIM TOP logo cast into the right side shell.
So much for that warranty sticker, oh well!
Internals Review
I won’t lie, I didn’t even see the warranty void sticker until long after having cracked open the shells. Ah well some sacrifices have to be made right?
As mentioned there is very little distinguishing this gearbox from a JG/clone shell from the outside, and the inside isn’t much different as far as the shell is concerned. AIM claims it is “Super Reinforced” and the inside shows the same as the outside with no internal reinforcements. This is really a debatable issue as most commonly “reinforced” shells fill the space around the gears with metal. This is a pointless reinforcement as no airsoft gearbox has issues with failures around the gears. However, version 2 gearboxes, like this one, DO have failures around the cylinder head area. The shell is a copy of the original Tokyo Marui design which is prone to failures under high stress such as high FPS or high Rate of Fire (RoF).
Another area of concern is always the choice of bushings or bearings. There is always an argument over which is better. Bearings offer lower resistance, but under stress can rupture and send ball bearings flying into the gearbox, damaging any number of parts. Bushings on the other hand are one piece of metal and cannot fail, but have a higher friction leading to more resistance for the motor to turn. Since this gearbox is destined for a low FPS/high RoF the included 8mm bearings are fine.
The selector plate is a standard polycarbonate and does the job. The only thing worth noting is the lack of a metal conductor on the selector plate as a secondary electrical cutoff.
The gears are a high torque setup included for the use of the stock M120 spring. The gears all appear to be made of powdered metal alloy fused together under pressure. This can be exceptionally strong if done correctly, but since this is China made the quality is questionable. However, for a M120 spring they are certainly more than strong enough. One thing I did notice however, was that the gears were bone dry, there was absolutely no grease on the gears, which is something that will have to be done if you wish to see any length of life out of your purchase.
Speaking of the spring, I was impressed with the feel of the spring, it felt like an M120 and looked like the oil quenched Guarder springs.
The spring guide was decently milled steel alloy with a bearing to reduce the chances of the spring twisting and catching as the gearbox cycles.
The rest of the internals were somewhat of a tossup.
I was extremely pleased with the cylinder head quality and the included double o-ring. While this may not be completely important, double o-ring heads make a much better and consistent seal over single o-rings. The cylinder was also a nicely polished chrome plated type 0 (no port) typical for a 455mm+ length barrel.
The tappet plate is a standard version 2 tappet plate, but was poorly cast and extremely rough. I spent some time smoothing some edges of casting marks for smooth operation.
The air nozzle was also somewhat rough and required minor sanding to smooth the movement. I was pleased however to find a o-ring inside of the nozzle for a solid seal to the cylinder head.
The piston was equally as rough as the other plastic parts. Once smoothed however, it cycled cleanly and I am fairly confident in its use. The full metal teeth make for a slightly slower RoF, but AIM/TOP has hollowed out large portions of the side walls to make up for the increased teeth weight. The piston head is a typical polycarbonate with a good quality #14 o-ring and bearing.
Performance
Usually with any gearbox I receive I’m always set to have to re-shim and re-lube the entire box. I was happy to find that the factory shimming was spot on, requiring only a complete lube as mentioned with the gears.
I was also happy with the factory air seal. There were zero leaks from the piston to the air nozzle.
The wiring felt like good quality and held up to the basic test.
RoF: 16RPS with a stock JG motor and 9.6v 1500mAh NIMH battery
FPS: 390FPS average over 10 shots
Typically a M120 spring will fire roughly 390-410FPS with a bearing on the piston head to spring guide. The average of 390FPS might be a tad low but there may have been a leak in the test hop up used, so expect slightly higher or lower numbers on your individual setups.
Final Thoughts and Upgradeability
Like any M4/M16 gearbox, the AIM/TOP can be installed in any variant. Since the gearbox is 100% TM compatible, any aftermarket parts can be installed.
Externals Score: 8/10
It’s not “super reinforced” so I will take some points for false advertizing. But it works.
Internals Score: 6/10
The rough plastic and lack of lubrication lose a couple more points. The missing pigtail with the battery connector also loses points as it is a necessary part of the wiring harness.
Overall score: 6/10
Since this was bought as a base for a custom rifle the negatives aren’t too important, however if you are new to upgrading and looking for a quick drop-in box this might not be the best choice out there.
© Copyright triggs 2012
AIM/TOP M120 “Super Reinforced” Complete Gearbox
- Overview
- Accessories
- Externals review
- Internals review
- Performance
- Final Thoughts and Upgradeability
Overview
As a custom airsoft gunsmith I’m usually against buying any pre-made gearboxes as they generally require more work than they’re worth. However, recently, individual products within the US have become harder, or more expensive, to find than a basic drop in gearbox. So I ended up picking up one of the AIM/TOP complete gearboxes for a custom built M4 for a customer.
Accessories
The AIM/TOP gearbox comes with literally no accessories. It comes in its box with good quality foam packing and that’s all.
I ordered a front wired gearbox as that was all the store had in stock at the time, and much to my surprise the box didn’t include the section of the wiring harness that includes the battery connector. If it wasn’t for the fact I was already planning on a custom wiring harness I would have easily been more annoyed.
Externals Review
Externally there’s very little to mention. While the box lists this as a “Super Reinforced” gearbox it’s clear from the outside there is no additional reinforcement compared to a standard Tokyo Marui gearbox, unlike the KWA 2GX shell I reviewed earlier.
The only thing distinguishing this gearbox from a JG/clone gearbox is the AIM TOP logo cast into the right side shell.
So much for that warranty sticker, oh well!
Internals Review
I won’t lie, I didn’t even see the warranty void sticker until long after having cracked open the shells. Ah well some sacrifices have to be made right?
As mentioned there is very little distinguishing this gearbox from a JG/clone shell from the outside, and the inside isn’t much different as far as the shell is concerned. AIM claims it is “Super Reinforced” and the inside shows the same as the outside with no internal reinforcements. This is really a debatable issue as most commonly “reinforced” shells fill the space around the gears with metal. This is a pointless reinforcement as no airsoft gearbox has issues with failures around the gears. However, version 2 gearboxes, like this one, DO have failures around the cylinder head area. The shell is a copy of the original Tokyo Marui design which is prone to failures under high stress such as high FPS or high Rate of Fire (RoF).
Another area of concern is always the choice of bushings or bearings. There is always an argument over which is better. Bearings offer lower resistance, but under stress can rupture and send ball bearings flying into the gearbox, damaging any number of parts. Bushings on the other hand are one piece of metal and cannot fail, but have a higher friction leading to more resistance for the motor to turn. Since this gearbox is destined for a low FPS/high RoF the included 8mm bearings are fine.
The selector plate is a standard polycarbonate and does the job. The only thing worth noting is the lack of a metal conductor on the selector plate as a secondary electrical cutoff.
The gears are a high torque setup included for the use of the stock M120 spring. The gears all appear to be made of powdered metal alloy fused together under pressure. This can be exceptionally strong if done correctly, but since this is China made the quality is questionable. However, for a M120 spring they are certainly more than strong enough. One thing I did notice however, was that the gears were bone dry, there was absolutely no grease on the gears, which is something that will have to be done if you wish to see any length of life out of your purchase.
Speaking of the spring, I was impressed with the feel of the spring, it felt like an M120 and looked like the oil quenched Guarder springs.
The spring guide was decently milled steel alloy with a bearing to reduce the chances of the spring twisting and catching as the gearbox cycles.
The rest of the internals were somewhat of a tossup.
I was extremely pleased with the cylinder head quality and the included double o-ring. While this may not be completely important, double o-ring heads make a much better and consistent seal over single o-rings. The cylinder was also a nicely polished chrome plated type 0 (no port) typical for a 455mm+ length barrel.
The tappet plate is a standard version 2 tappet plate, but was poorly cast and extremely rough. I spent some time smoothing some edges of casting marks for smooth operation.
The air nozzle was also somewhat rough and required minor sanding to smooth the movement. I was pleased however to find a o-ring inside of the nozzle for a solid seal to the cylinder head.
The piston was equally as rough as the other plastic parts. Once smoothed however, it cycled cleanly and I am fairly confident in its use. The full metal teeth make for a slightly slower RoF, but AIM/TOP has hollowed out large portions of the side walls to make up for the increased teeth weight. The piston head is a typical polycarbonate with a good quality #14 o-ring and bearing.
Performance
Usually with any gearbox I receive I’m always set to have to re-shim and re-lube the entire box. I was happy to find that the factory shimming was spot on, requiring only a complete lube as mentioned with the gears.
I was also happy with the factory air seal. There were zero leaks from the piston to the air nozzle.
The wiring felt like good quality and held up to the basic test.
RoF: 16RPS with a stock JG motor and 9.6v 1500mAh NIMH battery
FPS: 390FPS average over 10 shots
Typically a M120 spring will fire roughly 390-410FPS with a bearing on the piston head to spring guide. The average of 390FPS might be a tad low but there may have been a leak in the test hop up used, so expect slightly higher or lower numbers on your individual setups.
Final Thoughts and Upgradeability
Like any M4/M16 gearbox, the AIM/TOP can be installed in any variant. Since the gearbox is 100% TM compatible, any aftermarket parts can be installed.
Externals Score: 8/10
It’s not “super reinforced” so I will take some points for false advertizing. But it works.
Internals Score: 6/10
The rough plastic and lack of lubrication lose a couple more points. The missing pigtail with the battery connector also loses points as it is a necessary part of the wiring harness.
Overall score: 6/10
Since this was bought as a base for a custom rifle the negatives aren’t too important, however if you are new to upgrading and looking for a quick drop-in box this might not be the best choice out there.
© Copyright triggs 2012