G&P XM177E1 AEG Gearbox Disassembly

Last time, we showed you how to disassemble the exterior of the G&P XM177E1 and remove the gearbox.

This time, I'll take apart the gearbox I removed and examine the parts inside. And finally, I'll decide on the customization options.

Let's open the gearbox.

Unveiling the gearbox

Let's take a quick look at the gearbox before opening it.

This is a side view.

This is a standard Ver.2 gearbox. Previous G&P Ver.2 gearboxes had a large cutout behind the cylinder that exposed the spring, but this seems to have been removed in recent batches. From a strength perspective, I think this is a good improvement.

By the way, it says 28 years old, but what does that mean? (Does it simply mean they are 28 years old?)

It's on the opposite side.

It's secured with nine hexagonal bolts, so it feels like there's good surface pressure on the mating surfaces.

Next are the wiring and the QC mark.

Since it's front wiring, the wires are located at the front.

It has a QC mark, but will I be able to get a warranty in Japan? I'll probably just take it apart anyway, so I won't worry about it.

Let's take it apart.

Unfortunately, it doesn't use a spring QD system, so you'll have to open it the old-fashioned way, inserting a screwdriver behind the main spring.

Modern gearboxes have spring guides that fit snugly into the gearbox, so you might not even need a screwdriver.

It's finally being unveiled.

It's a mystery why the parts painted with the green alien grease are all over the place.

My initial hope that it might work right out of the box was quickly dashed; it seems best to re-grease it.

Next, let's take a look at each part in its original, uncleaned state.

Gearbox components

Let's start by looking at the gearbox casing.

Gearbox casing

This is the gearbox with all its parts removed.

There's quite a bit of bulk at the top of the gearbox, which I believe is to ensure fastening rigidity, similar to the ver.3 gearbox.

Furthermore, the bearings are 8mm 7-ball bearings, which is my favorite specification. Another clever feature of this gearbox is the grease reservoir shape for lubricating each gear and bearing. However, this is pointless as the grease is applied haphazardly right out of the box.

It's on the opposite side.

One thing that caught my attention was the elaborate design of the wiring routing.

However, I'm planning to switch to thicker 1.25 sq wiring, so some modification might be necessary.

Incidentally, it's manufactured using aluminum die-casting, but judging from the feel of the product, the mold seems to be showing some signs of wear.

As the mold wears out, the product becomes difficult to remove from the mold, resulting in scratches in the removal direction. This gearbox also had a few minor scratches (which do not affect performance).

Setting aside the out-of-the-box grease condition, the gearbox specifications seem quite good, so I have high hopes for customizing it.

Electrical system

Next, let's look at the electrical system.

First, here's the overall picture.

It doesn't have the trendy electronic triggers or even FETs; it's an old-fashioned electronic system.

Unusually for an overseas product, it comes with a fuse, but unfortunately it's a tube fuse and seems to have high resistance, so I'll replace it with a blade fuse.

The wiring looks like 1.0 sq rather than the more common 0.75 sq, but it doesn't seem to be of very good quality, so I'll rewire it with 1.25 sq.

Let's take a look at the Switch.

For some reason, instead of contact grease, there was a lot of regular grease that you'd find on gears and the like.

Of course, the insulation has no effect whatsoever, and it only slightly burns after a test firing, so countermeasures are necessary.

I'm trying to decide whether to use an FET or an SBD for the switch issue. Ideally, I'd like to use an FET, but it depends on the available space.

Intake and exhaust related parts

Let's start by looking at the piston, one of the intake and exhaust-related parts.

From the side, it looks like a normal piston. However, it has almost no grease applied to it.

正面です。

This is a rather unusual intake design. I'm not sure how it affects performance. I think a more conventional rear or side intake design would be better.

The piston head was secured in a different way: a hexagonal screw on the front and a slotted screw on the back.

It looks easy to disassemble.

Next is the piston rack gear.

Only the last two teeth on the piston, where it is released, were metal. Also, the gear count was reduced by one tooth to 14.

This specification seems good as it's unlikely to crash during the initial cycle out of the box, but the grease is terrible. It's pretty good, but in my case, I use one with all metal teeth on the rack gear.

Next is the cylinder head.

It was a standard cylinder head with a single O-ring for airtight sealing.

The back is also simply covered with rubber.

I like this standard type of cylinder head.

Next is the cylinder.

From the side, it looks like a perfectly ordinary cylinder.

This looks like a full cylinder, but if you look inside, you'll see that it's actually an acceleration cylinder due to the intricate machining process.

The effective cylinder length is adjusted by machining it with a taper. This taper machining is a fairly difficult manufacturing method. Perhaps because of this, the end of the taper is somewhat of an approximate dimension, but I don't think it needs to be finished precisely, so I think it's fine as is.

This is an interesting cylinder, so I'd like to use it.

Next is the nozzle.

The nozzle is made of machined aluminum and is quite short at 21mm, unlike the typical M4 type.

The specifications include a sealing nozzle with one O-ring.

The beveling at the tip is quite neatly done.

I quite like this type of nozzle, so I'd like to continue using it if it doesn't cause too many hop-related issues.

Finally, there's the main spring and spring guide.

The main spring was a short, unequal-pitch spring. It seems they've properly installed a spring specifically designed for the Japanese market.

The spring guide is made of iron, but for some reason it has a resin washer attached.

I think this resin washer/spacer is for adjusting the initial velocity, but I'm not entirely sure.

Next, let's look at the drivetrain components.

Drivetrain parts

Let's start by looking at gears, which are representative components of the drivetrain.

This is the sector gear.

The sector chip wasn't the shape I liked.

Judging from its appearance, the gear appears to be made by sintering. While sintering results in lower strength compared to forging, its excellent moldability allows for high precision, and the gear's tooth precision and shape seem to be of good quality.

This is a side view.

It appears that the pull gear has had about 2-3 teeth cut off. Indeed, with a stock cycle rate of 17.1 rounds per second, there's a slight possibility of crashing with a normal sector gear tooth count, so this might be a preventative measure.

This is the back side.

Next is the spur gear.

This is a standard gear, and there's nothing particularly noteworthy about it other than its relatively good tooth shape and precision.

tooth surface

back side

Finally, there's the bevel gear.

This was an excellent gear with eight latches to prevent reverse rotation.

This gear has a complex shape, so it appears to have been manufactured by machining. As a result, it has a very good shape.

Since engraving letters by machining is costly, the markings are stamped instead.

Finally, there's the anti-reverse latch.

I don't really understand the performance difference between the different shapes of this product, but since it's a latch, I think it's fine as long as it's lightweight and doesn't break.

remaining parts

Now that I've introduced the main components, let's take a look at some of the remaining components that caught my attention.

This is a tappet plate.

It's probably made of a nylon-based resin and has some flexibility. What I personally find disappointing is that the tappet blades are triangular, which is an unusual shape these days. I'm debating whether to modify them or use them.

The neck of the tappet is a very intricately shaped part, which is where the load is applied, and it is designed to provide rigidity.

The tappets are very well made, but the only thing I regret is the shape of the blades, which I'll think about later.

Next is the tappet spring. It has more coils and seems stronger than a typical one.

Next is the trigger and trigger spring. The spring is a little stiff.

The remaining parts—the selector plate, safety, and cutoff—didn't have any particularly noteworthy shapes, so I'll omit them.

That concludes our explanation of the gearbox components.

Summary

This is a summary of G&P gearboxes.

The individual components are quite well-designed and high-quality parts are used. The motor is a G&P M100, which is pretty good, and the increased rate of fire has been properly addressed. The shims are also properly included, and although there may be individual differences, the assembly was within an acceptable range.

One thing I forgot to check is that I didn't check the AOE (Area of ​​Effect) out of the box. If the AOE is severe and causes piston failure, the rack gear of the piston, which is made of weak resin, will break, so I don't think it will be a major problem.

Overall, it contains well-designed parts, but the unfortunate thing is the poor application of grease. If only the grease had been applied properly, it would probably be usable right out of the box, so it's quite a waste.

In conclusion, after disassembling it, it seems that simply applying grease should be enough for normal use.

Customization direction

The only request for the customization is simply to improve usability, so I'll weaken the spring in the delta ring of the handguard, and I'll also take some measures to address the fact that the electronics don't seem to be able to withstand the discharge of the LiPo battery.

In addition to that, I'll be doing my usual modifications to improve the responsiveness: changing the gear ratio, shortening the trigger, and changing the motor.

Regarding the ball flight, I'll be adjusting it using Miyagawa Rubber's reliable and proven long-range middle nitrile shaft with a hardness of 60.

I'll assemble it carefully, aiming for a performance of around 25 rounds per second with a muzzle velocity of around 92 m/s and 0.2g BBs and no hop-up.

Next time, I'll be introducing the customization section, so please stay tuned if you're interested.

It's debatable whether it's fully functional right out of the box, but it's a recommended product. However, perhaps due to the coronavirus, it doesn't seem to be imported into Japan in large quantities.

Therefore, I'll introduce some models that are in stock at the time of writing and that I personally like.

Basically, the latest production batch has the same internal components but a fantastic exterior, so it's recommended for anyone who wants a full-metal standard model.

G&P AR 9mm SMG AEG
A US military SMG from the Vietnam War era. The M16 receiver combined with the oddly sized 9mm magazine looks really cool.

G&P M16 Vietnam Version
This was a mainstay rifle from the same period as the XM177 series.

G&P M4A1 AEG Marine Corps Model
定番です。