The Airsoft AEG: A no-longer-brief overview of its glory

airsoft guns,airsoft aeg

This section will cover the airsoft AEG and its related internal parts.

First of all, some of you noobs might ask the question: what the deuce does AEG stand for? Answer: none of your business. Just kidding. AEG stands for Automatic Electric Gun, noobsie. But enough condescension.

For the more experienced audience looking for info on the AEG internal parts, click the following link to jump down to the more technical information HERE.

Let’s get mildly technical for a tick. While the AEG does incorporate a spring into its internal gearbox (aka mechbox), that spring cannot be pulled back to fire a BB without the power of the electric battery. Thus, it is an electric gun.

Truth be told, I’m a little bored already and am in need of some visual stimulation. What about you? Ok. Cool. Me, too.

Here’s a few airsoft AEG models that I am very fond of.

The M16

Electric M16 Airsoft Guns, Airsoft AEG

The M14

Airsoft M14 Rifle, Airsoft AEG

The M4

Airsoft M4 Rifle, Airsoft AEG

The M249 MkII (SAW)

Airsoft SAW, Airsoft M249, Airsoft AEG


Airsoft SCAR, Airsoft AEG

The AK47

Ak 47 Airsoft Guns

Here’s a couple Airsoft AEG styles that I am NOT fond of. At all. Whatsoever.

The Aug

Airsoft Aug, Airsoft AEG

The P90

Airsoft P90, Airsoft AEG

That felt good. Alright, back on track here. Most airsoft AEGs can switch between three modes:

-Safe Mode, where the weapon cannot be fired

-Semi-Auto, where the weapon fires a single shot with each trigger pull.

-Full-Auto, where the weapon can fire anywhere from a short burst to a long, string of BBs depending on how long you hold down the trigger.

In case you truly are a noob, I will tell you that the source of the electrical power to the gun comes from special battery packs.

So I should probably mention the manufacturers that make the best base AEG platforms in one aspect or another.

The industry standard or benchmark by which just about every other airsoft AEG is compared to are the guns from Tokyo Marui.airsoft aeg,tokyo marui logo
airsoft aeg,classic army logoYou’ll notice, if you haven’t already, that when looking for after-market parts to upgrade or replace in your rifle, many companies make their parts to fit the Marui rifles and/or Marui clones, like Echo1. I like the Echo1 models because they are generally compatible with most Marui parts, plus pretty much all their latest models that I can think of come stock with metal bodies, which gives the gun a more realistic look and feel, along with not one, but two magazines. They are a great value.airsoft aeg,king arms logo

G&P laser products logo,airsoft aeg

systema logo,airsoft aeg
Several other top-of-the-line brands include, in no particular order: G&P, King Arms, VFC, and Systema. Systema actually makes a different type of AEG altogether called the PTW, which stands for “Personal Training Weapon.” These rifles are pretty sweet for a number of reasons, and consequently will have their own page at some point. For now, just know that they are awesome, and expensive.

vfc logo,airsoft aeg


This is where things get more technical.

Perhaps one of the most critical parts of the airsoft AEG, when it comes to accuracy anyway, is the hop-up unit. The hop-up unit places backspin on the BB during flight to keep it airborne longer, thus increasing the weapon’s range while the inner barrel helps keep the BB on target. However, if your hop-up rubber is not set in position properly, having the most precision-made inner barrel in the world won’t help you a whole lot. It is because of this, I personally feel that between the two parts, the hop-up unit is probably of much higher importance to airsoft AEG accuracy than the inner barrel. Additionally, playing a smaller, yet important, role in the airsoft AEG’s accuracy is the Air Nozzle. The air nozzle performs a couple functions. One in that it acts as a sort of gatekeeper for the BBs to be fed from the magazine into the hop-up unit, where it will be fired from. Once a BB has been fed into the rifle, the air nozzle then helps to situate the BB against the hop-up rubber. There are several different designs of airsoft AEG air nozzles made by various companies, with the intent to help set the BB against the hop-up rubber in the same position every time. This, theoretically, is supposed to help increase the rifle’s ability to consistently hit its intended target more often. On top of all that, it’s incredibly important for the air nozzle to create an effective air seal between the cylinder head and the hop-up unit. If there’s a leak at either point, the airsoft AEG will lose velocity, consistency, and probably accuracy. See below for more intel on air nozzles and selecting the right one for your rifle.

What I think I’ll do now, is list the common internal airsoft gun parts of an AEG, starting from the inner barrel and ending with the battery. This will give you a pretty good idea about the parts inside the airsoft AEG gearbox and the things you can do to upgrade, repair, or just performance-tune your rifle a bit. Since this page started as a glimpse of the AEG and evolved rather quickly into an uber-knowledge enhancer (if I do say so myself), I’ve set up a table of contents below. Click any link that strikes your fancy and you will jump to that section. You’ll notice in each section there will be a link to jump back up here, in an effort to make your browsing experience easier.

Additionally, you’ll notice that I’ve listed airsoft AEG brand names underneath each picture. Those represent brands that I’ve either had a positive personal experience with or that I’ve read a large number of positive reviews about on the numerous forums I frequent. I have NOT received any kind of compensation by any of the companies listed to recommend their products. Maybe it might not be a complete brand list for each part, but it’ll be good enough to get you pointed in the right direction. As a special and very important side note: All of the parts listed below can be found inside just about every airsoft AEG out on the market at present. HOWEVER, there are several different airsoft AEG gearbox versions, depending on the model you have. Here’s a helpful chart of the common gearbox versions and motor length types. The only COMMON version I see not listed is the gearbox found in Classic Army M249s.

AEG Gearbox & Motor Length Chart
aeg gearbox chart,airsoft aeg

Jump to Motor Section
Image courtesy Arnie’s Airsoft

Version 1 AEG Gearbox
version 1 gearbox,airsoft aeg

Version 2 AEG Gearbox
version 2 gearbox,airsoft aeg

Version 3 AEG Gearbox
version 3 gearbox,airsoft aeg

Version 6 AEG Gearbox
version 6 gearbox,airsoft aeg

Version 7 AEG Gearbox
version 7 gearbox,airsoft aeg

I’ll try to note each part that has to be matched to your specific gearbox. But in case I forget one, just be aware of that and pay attention to what you’re buying. All major retailers are going to specify what gearbox version the part(s) is made for, so again I say, PAY ATTENTION. If a certain part is gearbox- or rifle-version specific, I will make a note in that part’s section that says, “This part is version specific.” You’re welcome.

Airsoft AEG Gearbox Section
Table of Contents:

Inner Barrel
aeg tightbore barrel,airsoft aeg

Hop-Up Bucking
airsoft aeg

Hop-Up Nub
airsoft aeg, airsoft hop up

Hop-Up Chamber
airsoft hop up, airsoft aeg

Air Nozzle
airsoft air nozzle

Gearbox Shell
airsoft gearbox shell,airsoft aeg

Selector Plate
airsoft selector plate, airsoft aeg

Tappet Plate
airsoft tappet plate, airsoft aeg

Cylinder Head
airsoft cylinder head, airsoft aeg

airsoft aeg,aeg cylinder

Piston Head
airsoft piston head,airsoft aeg

airsoft piston, airsoft aeg

AEG Spring
airsoft aeg spring,airsoft aeg

Spring Guide
airsoft spring guide,airsoft aeg

airsoft aeg,airsoft gears

airsoft switch assembly,airsoft aeg

Anti-Reversal Latch
airsoft anti-reversal latch,airsoft aeg

airsoft motor,airsoft aeg

deans connectors,airsoft aeg

airsoft nimh battery,airsoft aeg

Assembled AEG Gearbox
airsoft gearbox,airsoft aeg

Image Gallery
airsoft m4 custom,airsoft aeg

Inner Barrel
airsoft aeg

EdGI Barrels*
edgi barrel,airsoft

PDI Barrels*

Prometheus Barrels
prometheus inner barrels,airsoft aeg

DB Custom Barrels (if you can find any)

*I would peg these two companies (EdGI & PDI) as having the best airsoft AEG barrels in production. The DBC barrels are very good as well, but they’re no longer being produced. I would give the advantage to EdGI because they are substantially cheaper than the PDI barrels, for essentially the same precision quality.

Before selecting the length of your barrel, you’ll need to read the section below on AEG Cylinders.

Very important info resides there. Be advised.

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Hop-up Bucking & Barrel Ring
airsoft aeg

Guarder Bucking (Black rubber)
guarder intruder shop logo,airsoft aeg

Prometheus Bucking (Red rubber)
prometheus cylinder,prometheus hop-up,airsoft aeg

Some airsoft retailers mislabel this as a Nineball or Laylax bucking, but the official Laylax website has it listed under the Prometheus brand division. Just an FYI to clear up any confusion

systema logo,airsoft aeg

airsoft aeg,firefly logo

I personally use the Guarder and the Systema buckings and have had positive results, but would feel quite comfortable using the Firefly or Prometheus buckings as well, based on the numerous reviews I have read.

It is important to effectively seal your hop-up bucking around the inner barrel so that no air can escape between the barrel and the bucking while the AEG operates.

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Hop-up Nub
airsoft aeg, airsoft hop up

If you’re just going to replace your stock nub, then it doesn’t really matter what brand. But if you’re going to use an H-style nub with the intent of increasing your airsoft AEG’s accuracy, you’ll want to go with the Shredder’s Concave Spacer (SCS) Nub.

airsoft hop up,airsoft aeg
There is a bit of prep work that must be done for this nub to work effectively in your airsoft AEG. It is not simply a plug-and-play part.

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Hop-up Chamber
airsoft hop up, airsoft aeg

G&P Hop-Up Chambers
G&P laser products logo,airsoft aeg

King Arms Hop-Up Chambers
airsoft aeg,king arms logo

Systema Hop-Up Chambers
systema logo,airsoft aeg

Prometheus Hop-Up Chambers
prometheus cylinder,prometheus hop-up,airsoft aeg

This part is version specific.

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Air Nozzle
airsoft air nozzle

If you see a brand that makes an airsoft AEG nozzle and includes the phrase “air seal” in the description or title somewhere, it’s probably going to be good. YOU NEED THAT SEAL!!! It will increase your FPS and consistency.

guarder intruder shop logo,airsoft aegFor example, the Guarder Air Seal Nozzle is a good one to start with.

Here are some more models that work well:

Freedom Art Nozzles
airsoft aeg,freedom art logo

Deep Fire Air Nozzles
airsoft aeg,deep fire airsoft logo

I’ve seen this nozzle
referred to as the
Pakayama Craft nozzle.
I’m pretty sure
Pakayama=Freedom Art.
For Marui M4/16/14 ONLY

Systema Air Seal Nozzles
systema logo,airsoft aeg

PGC Air Seal Nozzles
airsoft aeg,perversity gun corporation PGC logo

Prometheus Air Seal Nozzles
prometheus cylinder,prometheus hop-up,airsoft aeg

You can also mod your nozzle to fit an o-ring. See the Airsoft Custom Gun Section for details. Honestly though. Airsoft AEG nozzles are like 15 bucks. Just buy one with an o-ring.

This part is version specific.

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Gearbox Shell
airsoft gearbox shell,airsoft aeg

Best bet is to leave your airsoft gearbox alone unless it breaks in some fashion. They have been known to crack in some airsoft AEG setups. In the event the gearbox DOES need to be replaced, I’d probably just go with the stock model that came with the gun, if you can find it. If you are running a Marui, Classic Army, King Arms or G&P airsoft AEG, it probably wouldn’t be very difficult to find a replacement from Spartan Imports or one of the major retailers out there. Some acceptable brands for airsoft AEG gearbox shells include the usual suspects:

G&P Gearbox Shells
G&P laser products logo,airsoft aeg

King Arms Gearbox Shells
airsoft aeg,king arms logo

Systema Gearbox Shells
systema logo,airsoft aeg

Guarder Gearbox Shellsguarder intruder shop logo,airsoft aeg

Systema DOES make complete drop-in gearboxes with all the parts installed and ready to go in them for Marui-compatible M4/M16 & G3 AEGs. However, I’ve read mixed reviews on them. Mostly on the negative side. I’m only recommending the shell here.

This part is DEFINITELY version specific.

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Selector Plate
airsoft selector plate, airsoft aeg

Yes, this can break and is replaceable. Stick with the company that made your AEG, or upgrade to a Guarder.

This part is version specific.

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Tappet Plate
airsoft tappet plate, airsoft aeg

Same thing goes for the tappet plate, although there are some after market companies that make them. I’d go with Guarder or any of the previously mentioned brands that might produce one.

This part is version specific.

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Cylinder Head
airsoft cylinder head, airsoft aeg

Guarder Cylinder Heads
guarder intruder shop logo,airsoft aeg

Prometheus Cylinder Heads
prometheus cylinder,prometheus hop-up,airsoft aeg

Systema Cylinder Heads
systema logo,airsoft aeg

Here’s a friendly reminder to pull your head out of dark places when selecting a cylinder head. It’s usually best to match the brand of your cylinder head to your cylinder. Additionally, it would probably make your life easier if you not only matched brands, but if you have or are planning on purchasing an airsoft AEG “bore-up” cylinder, you’ll want to get the corresponding “bore-up” cylinder head. Best option is to go with a company that makes a “bore-up cylinder kit” that packages everything you’ll need for such a setup all together.

This part is version specific.

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airsoft aeg,aeg cylinder

Guarder Cylinders
guarder intruder shop logo,airsoft aeg

Prometheus Cylinders
prometheus cylinder,prometheus hop-up,airsoft aeg

Systema Cylinders
systema logo,airsoft aeg

Need I say more?

Actually, in this case: I do. So I’m glad I asked. Technically, you, my beloved reader, should be glad, too. I need to tell you about a tricky little situation involving the selection of a proper cylinder in order to optimize your setup’s performance. So grab a Snickers Bar and sit tight. And yes, it DOES matter what cylinder type you have in your airsoft AEG.

So let’s say you want to take your stock inner barrel, and replace it with a barrel from the approved list of Barrel vendors above (I would expect) that not only has a smaller inner diameter than your stock barrel, but it is longer in length. Well, you’ve now changed the volume characteristics of the rifle’s internals. The air volume in the cylinder needs to be properly paired with the air volume of the inner barrel (which is also technically a cylinder). I don’t care what you are or who you’ve done (what?), because of the numerous variables involved in the airsoft AEG’s internal component system, you’ll never quite get it perfect. However, if you tune your rifle well enough, you can get pretty darn close.

So how do you pick the right cylinder for the type of barrel you have? Wow! I’m asking great questions right now. You are, again, very welcome. In addition to barrel volume, you’ll “mos def” need to take a few other factors into consideration before making your decision on cylinder type. Those factors include, but are not limited to, the weight of your preferred BB, spring strength, and piston stroke length (for those of you that short-stroke your rifles).

I can get all technical here and layout out various calculations for volume and ratios….so I will.
cylinder volume diagram,airsoft aeg

Why in the WORLD am I dropping knowledge bombs on you regarding cylinder volume formulas? Well, other than the fact that I love solving for X, you should probably be aware of the volume ratio between your cylinder and barrel, because if it’s not properly balanced, your airsoft AEG probably isn’t performing to its full potential. And the thought of that just REALLY bums me out.

In order to calculate your cylinder to barrel volume ratio, you’ll first need to calculate the ratio of both parts by measuring each of their radii, along with each of their heights. Remember that the radius = half the diameter, so the easiest way to figure either radius accurately would be to measure the cylinder and barrel diameters and then divide by two for each. You’ll need to measure your cylinder’s volume with the cylinder head installed, so that its occupation of space inside the cylinder can be taken into account. Additionally, if your cylinder is ported, you only measure the height of the cylinder for volume purposes from the cylinder head to the point where the port begins. *Special note for you short-strokers* Pay attention to your piston’s stroke length on ported cylinders. If the stroke length does NOT extend beyond the beginning of the cylinder port, you’ll need to measure Height (h) from the cylinder head to the farthest point at which the piston reaches (half-cycle) before it changes direction to propel the BB downrange and complete a full cycle. Refer back to ported cylinder illustration in the diagram above for a little more visual clarity.

And now a message from Captain Obvious: “Your inner barrel diameter (r x 2) (6.01mm, 6.03mm, 6.04mm, etc) and Height(h) (509mm, 450mm, 363mm, etc.) have already been determined for you by the manufacturer of said barrel.”

Remember that both values were on the package label and description of the website you probably bought it from? If you don’t remember your inner barrel’s diameter when you bought it, the designated FAIL area just became that which you are occupying. You need to know what you’ve got going on inside your AEG. Situational awareness is a beautiful thing. While those that know me can tell you that there are some situations when my awareness is nonexistent, not knowing the specs of my airsoft AEG parts is not one of those situations nor should it be in your case either. End of tangent.

K. So once you’ve measured and calculated the two volumes, then take the volume of your cylinder volume and divide it by your barrel volume. (Cylinder_Volume/Barrel_Volume). The resulting number, or quotient, is your cylinder to barrel volume ratio. Typical ratios are generally between 1.5:1 and 2:1, with cylinder volume being the greater of the two.

Now, let’s say you get your ratio balanced to a satisfactory level but then you want to upgrade your spring to gain some range on the OPFOR.

The general rule is that as you increase the spring strength, you need to increase your cylinder to barrel volume ratio as well.

You can do this in several ways. One is to upgrade to what’s called a “Bore-Up” Cylinder, which gives you more actual cylinder volume than a normal after-market cylinder would. If you’ve already done this prior to upgrading your spring, then two other options you can do include either cutting your inner barrel down and/or using a heavier BB.

Despite the common mentality that, “longer is better,” reality and science say that’s not necessarily the case.

Wait…are we still talking about airsoft AEG barrels here? Actually, yes we are, but I wanted to take the opportunity to make a cleverly ambiguous statement with a hint of adult innuendo for the purpose of amusing myself. Also, in reference to using a heavier BB, you really shouldn’t be using anything less than a .25g BB to begin with, regardless of how hot (or not) your airsoft AEG shoots, but that’s an entire conversation of its own that will be discussed elsewhere. In terms of tuning your system, having a high Cylinder to Barrel volume ratio, say 4:1 or so with a lightweight BB (< .25g), will quite possibly result in wasted energy that does not get transferred. So by increasing the weight of the BB you’re using, you can gain more efficiency back if you plan on keeping that cylinder-barrel volume ratio in tact. Well-made, heavy BBs are generally better to use in a open field environment, as the weight of the BB helps to stabilize the BB during flight, thereby helping out your accuracy. So there’s more than one benefit to increasing BB weight.

Unfortunately, there’s no set guide, table or chart that provides a specific ruling on the perfect combination between barrel length, cylinder volume (which can be affected by piston stroke length), BB weight, and spring strength. It also depends on what purpose you desire your AEG to serve (assault, support, marksman, etc). Like I said earlier, those aren’t even all the variables in this whole equation. Other factors in addition to the ones already mentioned, some of which would be pretty difficult to measure for most, include hop-up and barrel friction, efficiency of your air seals at points like the cylinder/cylinder head, piston head o-ring, air nozzle around the cylinder head port, air nozzle against the hop-up unit, and seal around the hop-up rubber itself. Not to mention the weight of your piston set (piston + piston head). As you can see, there are many internal variables, making everyone’s setup at least slightly different. Therefore, you’ll just have to go the Trial-and-Error route to find out what works best in YOUR system. Doing this definitely constitutes “tuning your rifle” and if you want your airsoft AEG to be the best it can be, then you’ll want to give this a shot.

Here are the Airsoft AEG Cylinder models that I recommend and the corresponding inner barrel lengths they should be paired with.

Standard Bore:

prometheus cylinder,prometheus hop-up,airsoft aegPrometheus Stainless Hard Cylinders:

Prometheus Stainless Hard Cylinder
(A) for 451 – 550mm length barrels

Prometheus Stainless Hard Cylinder
(B) for 401 – 450mm length barrels

Prometheus Stainless Hard Cylinder
(C) for 301 – 400mm length barrels

Prometheus Stainless Hard Cylinder
(D) for 251 – 300mm length barrels

Prometheus Stainless Hard Cylinder
(E) for 201 – 250mm length barrels

Prometheus Stainless Hard Cylinder
(F) for 110 – 200mm length barrels

systema logo,airsoft aegSystema N-B Cylinders:

Systema N-B Cylinder Type-0 ( ZS-04-16 )
for M16A1/VN/A2/G3/SG550/AUG series-length barrels

Systema N-B Cylinder Type-1 ( ZS-04-17 )
for AK47/XM177/SG551 series-length barrels

Systema N-B Cylinder Type-2 ( ZS-04-18 )
for MP5A4/A5/SD5/SD6/MC51 series-length barrels

Systema N-B Cylinder Type-3 ( ZS-04-19 )
for PDW series-length barrels

Systema N-B Cylinder Type-4 ( ZS-04-20 )
for MP5K series-length barrels

guarder intruder shop logo,airsoft aegGuarder Cylinders:

Guarder Cylinder ( GE-03-01 ) for G3/M16A2/AK series-length barrels
Guarder Cylinder ( GE-03-02 ) for M4A1/SR16 series-length barrels
Guarder Cylinder ( GE-03-03 ) for MP5A series- and SD series-length barrels
Guarder Cylinder ( GE-03-04 ) for MP5K/PDW series-length barrels

For use with 120 spring or higher, optimized inner barrel length, & .27g BB or heavier.

guarder intruder shop logo,airsoft aegGuarder Bore-Up Cylinders:

Guarder Bore-Up Cylinder ( GL-03-01 )
for Marui G3/M16A2/AK series-length barrels

Guarder Bore-Up Cylinder ( GL-03-02 )
for Marui M4A1/SR16 series-length barrels

Guarder Bore-Up Cylinder ( GL-03-03 )
for Marui MP5A4/A5 series-length barrels

Guarder Bore-Up Cylinder ( GL-03-04 )
for Marui MP5K/PDW series-length barrels

systema logo,airsoft aegSystema New Bore-Up Cylinder Sets:

Systema New Bore-Up Cylinder Set ( ZA-03-05 )
for G3A3/A4/SG1 series-length barrels

Systema New Bore-Up Cylinder Set ( ZA-03-04 )
for AK47/AK47S series-length barrels

Systema New Bore-Up Cylinder Set ( ZA-03-34 )
for M16A2 series-length barrels

Systema New Bore-Up Cylinder Set ( ZA-03-38 )
for M4-A1 series-length barrels

Systema New Bore-Up Cylinder Set ( ZA-03-40 )
for MP5 series-length barrels

This part is version specific.

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Piston Head with Ball Bearing
airsoft piston head,airsoft aeg

Those brands all make piston heads that are vented/ported on top. This allows air to rush inside the head, expanding the o-ring to create a better seal against the cylinder. A better seal inside the cylinder creates better compression, which is basically what keeps your FPS consistent from shot to shot, not to mention the little boost in FPS you’ll probably get.

Additionally, they all have bearings attached. The bearing piece relieves unnecessary tension from the spring torquing during operation. See also, the bearing on the Spring Guide Rod. Same function, just from the other end.

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airsoft piston, airsoft aeg

Ah yes. The airsoft AEG piston. It’s been said by pretty much all of my Airsoft mentors (yes, I not only have one, but several) that the piston should be the weak point in your gearbox. Rest assured, at some point after enough use, something inside your gearbox will strip (not in a good way). It could be your gears, the motor pinion gear, or the piston. The piston is probably the best option to have get toasted, as it is the cheapest and easiest to replace. The pinion gear isn’t expensive, but it’s a bit more difficult to install while the gears are usually substantially more expensive to replace. Especially if you’re running a Designated Marksman Rifle (DMR) with a set of gears like the Prometheus Double Torques or the Systema Infinite Torque-Ups. SO. What am I getting at here? Well, my friend and favorite reader, there are essentially two common material types that make up an airsoft aeg piston. You’ll see aluminum metal aeg pistons and you’ll see polycarbonate, or polycarb, aeg pistons. Although polycarb pistons are technically a type of plastic or something very similar, certain companies make a very sturdy polycarb piston that hold up quite well under a heavy load of stress. Those companies are:
Guarder grey piston. (are you starting to see a trend here?)
The Guarder will NOT fit in certain Classic Army rifles

G&P white piston. This is a great piston for Classic Army rifles

Systema polycarb


I will say that I do currently run an aluminum piston in my DMR and have had zero issues with it. However, as with just about every airsoft product out there, your mileage will, again, vary. It’s only a matter of time before something in my gearbox takes a dump because of that piston, but I like to live on the edge. A safer, more conservative bet would be to run one of the three brands/models I’ve listed above.

Piston Head Attached to Piston
airsoft piston head, airsoft piston,airsoft aeg

This is just a shot, for illustrative purposes, of what the piston head looks like when it’s been attached to the piston.

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AEG Spring
airsoft aeg spring,airsoft aeg

While there are usually a multitude of different springs inside just about every airsoft gun, when someone is referring to THE AEG spring, this is more than likely what they’re referring to. It is this spring from which the AEG derives the majority of its power from. Yes, you can gain little bits of velocity boosters from adding certain parts and modifying others, but this is the main source of the proverbial FPS (BTW, that means feet-per-second, for the noobs. “BTW” means by the way, for the old people). I’ve used a number of different brands and strengths of springs, from PDI, to Guarder, and Systema to name a few. Speaking of which, you’re pretty much golden with any of those brands when it comes to any part. But specifically in the case of the AEG spring, yes, they’re all good. I prefer the Guarder or Systema over the PDI. I felt like I got more power from the former two than I did from the PDI. However, I got the best results (most power) from the Airsoft Surgeon springs.

For all non-noobs, skip ahead to something else. For all you noobzors, pay close attention. There are a number of different levels you can achieve in an airsoft AEG, it just depends on the strength of spring you choose. Check out this chart from as a general reference point:

airsoft aeg

It should be noted that just throwing in a new spring, like one of the ones mentioned on the chart, does NOT immediately guarantee that your airsoft AEG will operate at the stated velocity levels. As you can see from this highly informative, not to mention lovely, web page, there are a bunch of variables going on inside the weapon that can affect your power and accuracy, both positively or negatively.

I recommend the following brands for airsoft aeg springs:

Airsoft Surgeon

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Spring Guide Rod with Ball Bearing
airsoft spring guide,airsoft aeg

Brand doesn’t matter a whole lot as long as the spring guide corresponds with your gearbox version and that it has a bearing to help alleviate that unnecessary torque tension I spoke about earlier, in the Piston Head section above.

I use the Guarder spring guide with bearing, of course.

This part is version specific.

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airsoft aeg,airsoft gears
Photo from Airsoft Mechanics

All three gears are version specific.

While each of the following three gears is replaceable separately, you can also acquire them together as a set. Usually purchasing the set is the way to go. As a general rule, they all need to be upgraded if you’re attempting to enhance the performance of your Airsoft AEG. One important factor that a lot of players overlook when acquiring a gear set is the ratio of the gears they are purchasing and whether that is the correct ratio for the type of performance they are looking to accomplish. The number of teeth on each gear in the set will determine the ratio and in effect, determine the type of Airsoft AEG system they should be used for. Unless I’m incorrectly recalling the info I’ve researched on this, the gear ratio is an indicator of how many times the gears have to make a complete cycle or rotation in order to cycle the piston (which is a rack gear, in and of itself) one time.

Here’s an extremely useful chart created by an extremely sharp fellow who calls himself RiotSC over at the Airsoft Mechanics forums. Special note on Riot and his Siegetek Concepts (SC) Airsoft AEG gear sets. You’ll see down below that I’ve gone ahead and included his brand of gears among the current industry titans that we all know and love (except for those who know better). I included his gears in my list of recommendations because in all likelihood, they are probably going to be the best Airsoft AEG gears currently on the Airsoft market. While I’ve not had the chance to try out his gears, I’ve read the testimonials, examine the pictures, and followed many of Riot’s posts in the A-M forums. I’m willing to bet the cost of a set of his Torque gears that they will probably rock face. He’s gone ahead and made a number of subtle changes to the leading existing designs that achieve not-so-subtle performance enhancements. This isn’t to say that he’s just copied what others have done and made some tiny changes, he’s also using some pretty insane materials that most Asian manufacturers wouldn’t dare touch because it would cost them more than a handful of Yen to produce. And then there’s the Cyclone Dual-Sector Gear he designed for Uber-High-Speed/ROF setups. It’s just better if you check the link for the broadening of your horizons. There’s literally nothing else like it on the market. Crazy/innovative stuff he’s come up with.

airsoft aeg,airsoft gear ratio chart

While this chart does not include all gear sets on the market, it does include the top brands that I recommend based of performance reviews, personal experience and overall reputation. The chart is pretty self-explanatory once you read the little asterisks at the bottom. So do that before you try and interpret WTF is going on in the chart. In the essence of full disclosure, it should be noted that the chart’s creator DOES have a vested interest in the data found therin because of the fact that he’s using the chart to highlight the advantage his Siegetek Concepts (SC) Gears have over the competition. HOWEVER, it’s data that can’t be faked without the author being caught very easily so I highly doubt he’s trying to pull a fast one on any of you “skeptics” out there. If you’re an idiot and STILL don’t trust me, OR RiotSC, you can calculate the ratios to see for yourself, and then once you realize that I’m right about Riot being right, then you can know that the right thing to do would be to slap yourself. Trust me. I love Airsoft too much to lead you astray here. Here’s how to calculate your gear set’s individual and overall:

airsoft aeg,airsoft gears Count the number of teeth on the bevel gear that are engaged by the motor pinion gear. For the sake of example, we’ll say there are 30 teeth(I didn’t actually count the teeth in the pic).

Motor Pinion Gear Count the number of teeth on the motor pinion gear.
There are 10 teeth pictured here.

Now, divide the number of Bevel teeth (30) by the number of Motor Pinion teeth (10). 30:10 = 3:1 ratio. This number is your Bevel to Motor Pinion Ratio.

airsoft aeg,airsoft gears Count the number of teeth on the Spur gear that are engaged by the Bevel gear.
Let’s say there are 46 teeth.

airsoft aeg,airsoft gears Count the number of teeth on the Bevel gear that engage the Spur gear.
We’ll say there are 9 teeth.

Divide the Spur gear teeth (46) by the Bevel gear teeth (9). 46:9 = 5.11:1 ratio. This is your Spur to Bevel Ratio.

airsoft aeg,airsoft gears Do the same procedure for the Sector to Spur ratio.
Sector Gear Teeth engaged by Spur Gear:
We’ll say 32 teeth here, just to keep things moving.

airsoft aeg,airsoft gears Spur Gear teeth that engage the Sector Gear:
We’ll say 22 teeth here.

Sector Gear Teeth (32) divided by Spur Gear teeth (22). 32:22 = 1.45:1 ratio. This is the Sector to Spur ratio.

Now take the three ratios you just calculated above and multiply them together.

3 x 5.11 x 1.45 = 22.23

This is your final ratio for the whole gear set. This is the number that tells you whether your gears are better for high-speed setups (the lower the better), high-torque setups (the heavier spring, the higher the ratio needs to be), or if the ratio falls in the middle of the pack, basic upgraded assault rifle setups shooting around 400 fps with a .20g BB (1.47 Joules). Based on the ratio that we (Actually, it was just me. You just sat there while I did all the legwork) calculated above for illustrative purposes, 22.23 falls near the middle of the pack according to RiotSC’s Gear Ratio Chart. It actually leans a bit more towards lower-torque, higher-speed. So you’ll probably want to use a gear set with that ratio with an assault rifle setup, running a 110 or 120 spring. It’s probably not going to be the best set for running a high ROF rifle like a support weapon. As you can see from the chart, there are gear sets readily available that have much better ratios for high speed setups. High-Speed Gears:

If you’re looking to run an airsoft SAW or some other type of airsoft support weapon that requires a high ROF on full auto, then you’ll want a “High Speed” set of gears that has a low ratio. These High Speed gears are relatively smaller in size and have a lower amount of teeth, allowing the sector gear to complete a full rotation cycle without requiring as many revolutions from the motor pinion gear as a High Torque gear set would. The sacrifice in the high speed gears is that they cannot handle a high torque load, and therefore they are NOT suitable for airsoft AEGs running heavy springs. Usually a rifle running anything higher than a 120 spring is NOT a good candidate for the low-torque, high-speed gear sets. Additionally, you’ll need a high-speed motor to go with your low-ratio gears. High-Torque Gears:

For airsoft AEGs with heavier springs (e.g. a 130 equivalent and higher), pairing that type of spring with a high-torque (read: high ratio) gear set will yield satisfactory results. The give and take with high-torque gears is that they have the higher ratio of motor revolutions per sector gear cycle, thereby reducing the weapon’s ROF, BUT they can handle the much higher torque-load required by heavily upgraded, long-range airsoft AEGs. So if you’re looking to build a proper DMR or Semi-Auto Sniper Rifle, you’ll most certainly need a high-torque gear set. Pair that set with a high-torque motor and then say, “Thanks for making my AEG awesome, Airsoft-Obsessed!” Depending on my mood, I may or may not say, “You’re welcome.”

High quality gear sets for airsoft AEGs can be found from the likes of:

Siegetek Concepts (The “SC” in RiotSC)
siegetek concepts,riotsc,airsoft aeg, airsoft mechanics

Prometheus (Laylax)
prometheus gears,laylax gears,prometheus logo,airsoft aeg

Guarder Intruder Shop
guarder gears,guarder logo,airsoft aeg

systema gears,systema logo,airsoft aeg

G&P laser products gears,G&P laser products logo,airsoft aeg

Sector Gear
airsoft sector gear,airsoft aeg

One of the three gears used in the gearbox of an airsoft aeg. This is the gear whose teeth are used to engage the piston by pulling it back against the tension of the aeg spring mentioned above, to propel the BB towards your intended target.

There’s a special mod you can do for airsoft SAWs or any other aeg whose ROF (Rate of Fire) you wish to increase. It’s called Short-Stroking and it involves the Sector gear, along with the piston.

Additionally, if you’re having issues with your AEG not feeding BBs well, you can try adding a Sector Gear Clip.

airosft aeg,sector gear clip

As you can see, it just slips onto the knob that engages the tappet plate and you’re good to go. I have used this part to successfully resolve the BB feeding issues I was having in one of my rifles.

Spur Gear
airsoft spur gear,airsoft aeg

The Spur Gear is the middle gear, between the Sector Gear and Bevel Gear. It’s funny the Airsoft Gods would refer to it as a Spur Gear because the gear itself is very spur-like, with its teeth sticking out all around it…like a spur. Most peculiar….

Bevel Gear
airsoft bevel gear

The Bevel Gear is the one that gets engaged by the motor’s pinion gear.

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Anti-Reversal Latch/Lever
airsoft anti-reversal latch,airsoft aeg

Stick with the stock latch unless it starts wearing down or somehow breaks. If it does need replacement, you can find quality parts from some familiar names:

Deep Fire
This part is version specific.

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Switch Assembly (Trigger Unit) with Wiring
airsoft switch assembly,airsoft aeg

Over time and heavy use, your switch assembly in part or whole can wear out. Luckily there are plenty of replacement options. Take a guess at who makes some nice sets?
For those that haven’t been paying attention whatsoever to the rest of this page, I’ll enable you to continue being oblivious:
King Arms

This part is version specific.

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airsoft motor,airsoft aeg

So we’ve come to another very important part of the airsoft AEG internals. The AEG motor. Essentially, current after-market motors are designed to function in one of two environments:

High-Torque Motors:
One environment involves high torque, where the motor is required to pull back a heavy spring (120 or higher) for airsoft AEGs upgraded to fire long-distances (relative to airsoft ranges) and are usually kept on semi-auto firing mode. These AEG rifles are generally classified as Designated Marksman Rifles or semi-automatic sniper rifles, depending on the range of the weapon itself. These motors are generally designated as “torque-up” motors or some similar variation of that name.

One of the following motors should be used if you wish to run a rifle with a 120 spring or higher:

Guarder Infinite Torque-Up Motor
guarder infinite torque-up motor,airsoft aeg guarder infinite torque-up motor,airsoft aeg

Systema Magnum Motor*
systema magnum motor,airsoft aeg systema magnum motor,airsoft aeg systema magnum motor,airsoft aeg

*I am including these motors on my recommendation list because they are so well known. However, they are somewhat controversial in regards to their cost vs. value. There are those that have done very in-depth reviews of the Systema Magnum Motor and determined that they are pretty over-hyped in terms of their performance. Of course, there are plenty of others who swear by these motors and have not had a single failure. So, for now, I will keep them here. However, I am aware that there may be cheaper alternatives to the Systema for essentially the same performance level but possibly better quality. If that is the case, I plan on including those options here as soon as resources (time and money) become available. I really DO love Airsoft (and you, since you probably love it, too).

G&P M160 Turbo Charger Motor
G&P m160 motor,airsoft aegG&P m160 motor,airsoft aeg

King Arms Infinite Torque-Up Motor
king arms infinite torque up motor,airsoft aegking arms infinite torque up motor,airsoft aegking arms infinite torque up motor,airsoft aeg

You’ll need to refer to this chart to determine whether your rifle requires a long-, medium-, or short-type motor.

Also, if you’re the forgetful type or just haven’t seen it yet, review the Gears section regarding selecting high-torque gears.

***Some of you out there might say that running an “Infinite Torque-Up/Magnum” motor is WAAAAYYYY too much overkill for running a 120 spring. My response: pish posh!!! With a proper battery and a powerful motor, one will enjoy a lovely trigger response time on their airsoft AEG. And let me tell you about lovely trigger response time. It’s lovely. I’ll say that much. Additionally, I’d rather have a surplus of power rather than a shortage. But maybe that’s just me. I don’t know about anyone else. I’m not Miss Cleo.***

High-Speed Motors:
The second environment the AEG motor is designed for involves running the rifle on full-auto with a high rate of fire, where the motor is required to cycle the piston at high speeds. High-Speed motors are not built to handle a whole lot of torque, so running anything heavier than a 120 spring with a high-speed motor is NOT advisable (as in, DON’T DO IT). You’d be defeating the purpose of the high-speed motor by running a heavy spring because heavy springs will slow down the ROF.

Additionally, if you’re going for the high-speed (high ROF) approach, you’ll want to read the Gears Section above, if you haven’t already. In particular, read the part about installing “high-speed gears” with a low ratio (13:1-17:1) in order to maximize your rate-of-fire. When selecting a high-speed motor, I recommend the following models:

Guarder High-Speed Revolution Motor
guarder high speed revolution motor,airsoft aegairsoft aeg,guarder high speed revolution motor

Systema Turbo Motor
systema turbo motor,airsoft aegsystema turbo motor,airsoft aeg

G&P M120 High-Speed Motor
G&P m120 high speed motor,airsoft aegG&P m120 high speed motor,airsoft aeg

In case you’re not comprehending what I’m getting at,

High-SPEED motors should be paired with high-SPEED gears.

High-TORQUE motors should be paired with high-TORQUE gears.

Weird how that works.

This part is version specific (Long-, medium-, or short-type).

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Tamiya Connectors
tamiya connectors,airsoft aeg

Deans Connectors
deans connectors,airsoft aeg

Most airsoft AEGs come stock with the Tamiya Connectors, pictured on the left. I hate tamiya connectors for a couple reasons. One being that, by design, they are difficult to connect and disconnect from the rifle either because the white-ish plastic you see in the pic is poorly made or because it MELTED TOGETHER during operation because it sux and couldn’t handle the electrical heat being transferred from the battery to the AEG’s internal wiring. The second reason is they, again by design, don’t always provide a positive connection between the battery and the rifle, thereby causing your AEG not to function. This is lame. Do yourself a favor and, either you or someone else who’s handy with a soldering iron, install a set of the deans connectors. As a general electrician’s rule, the female dean’s connector goes on the battery and the male end goes on the AEG wiring (prongs go toward the power source). I’m going to take this opportunity to point out what should be somewhat obvious to those of you who have taken a biology class and have an imagination. An easy way to remember which is which is the male connector has the prongs, like an appendage exclusive to the male biological “crotchal region.” Those male prongs are inserted into the holes (the proverbial “hoo-hoo”) of the female connector. Just like sex. Enjoy that mental image.

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Nickel Metal Hydride (NiMH) Battery
airsoft nimh battery,airsoft aeg

Lithium Polymer (Li-Po) Battery
li-po battery,airsoft aeg

You’ll need a battery to operate your airsoft AEG.

Deciding on a battery depends on the characteristics of your rifles internal components. Personally, I just use Li-Pos of various sizes to power all my rifles, regardless of whether it’s shooting sub-400fps or 500+fps. That way I’m only charging one type of battery and I don’t have to worry about it. Perhaps the aspect that attracted me to Li-Pos initially was their high-voltage (11.1V) yet they came in compact sizes, unlike the high-voltage (10.8V+) NiMH batteries that were usually too big to fit in any of my rifles, even with a low mAH rating. So between the high-voltage, large energy storage capacity, and compact physical size, I was hooked. There was just too much convenience for me to go with any other battery type. I will admit that I was intimidated by the Li-Po battery type at first due to all the warnings that are out there about them. However, I’ve found that if you invest in a quality Li-Po Charger along with a balancer (good chargers usually come with an on-board balancer), there’s really not much to worry about on that end. The only other issue is over-discharging the battery below a certain voltage point (I wouldn’t recommend anything lower than 3.7V). So I simply purchased several batteries that work with my various setups and just use one per game. I have yet to get anywhere near the danger zone. Check out the Batteries Page for more details on airsoft AEG batteries.

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Here’s a shot of an almost fully-assembled AEG version 2 gearbox, found in most M4/M16, MP5 and G3 variants.

airsoft aeg, airsoft gearbox

Photo Courtesy AJPadre

This is what the inside of the gearbox looks like, with the exception of the missing half of the gearbox shell.

Thanks to the fine folks over at, you can watch an animated illustration of just exactly how all those parts listed above work together to propel those BBs downrange. Check it out here. Truth be told, I learned how to properly disassemble my very first airsoft AEG gearbox by watching their very informative videos.

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So, some of us know that the airsoft AEG pics I posted at the very top of the page are just the tip of the iceberg when it comes to the diverse array of rifle variations out there. Just the M4 alone has countless configurations. The airsoft industry is flooded with some very cool after-market parts to customize the look of your AEG. There are a number of companies that will build airsoft custom guns and sell them. Some are pre-made. Some are made to order. It all depends on who you’re dealing with. To give you just an ever-so-slight glimpse of the kinds of things you can do with your airsoft AEG, I will include some shots of rifles found in the various picture threads of a few of my favorite airsoft forums that have been externally modified or enhanced by the aforementioned “after-market” parts now (none of these rifles are mine, nor did I snap the photographs of any rifle featured):

Gunshell’s M14 EBR
airsoft m14 rifle,airsoft m14,m14

M4s + SR25
m16 airsoft gun,electric m16 airsoft gun

Luke_Martin’s M4
airsoft m4 rifle,airsoft m4

Drake’s SCAR-L
airsoft aeg

MP5 Variants
airsoft mp5,airsoft aeg

AK Variant
airsoft ak47,airsoft aeg

Wupjak’s AK74
airsoft ak47,airsoft aeg

AK Variants
airsoft ak47,airsoft aeg

Bizkitcan’s M4
airsoft m4,airsoft aeg

Siam79004’s M4
airsoft m4 custom,airsoft aeg

Kapitan_Jay’s Dragonov
airsoft dragonov,airsoft aeg

KA M4 w/VLTOR Stock
vltor m4 airsoft,airsoft aeg

I suppose that’s all I can think of for the Airsoft AEG section, at present. I’ll be adding more at a later time, so pay attention to my News & Updates Page for new content added. If there’s some piece of information you think should be on this page to help it become more complete, send me the info on my Contact Page and I’ll consider adding it. Assuming it’s not complete rubbish, of course. Otherwise, click the link below to return home or the links up top to head to another section.

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  • Brenna Vegas - This is the right site for anyone who really wants to find out about this topic. You understand a whole lot its almost hard to argue with you (not that I actually would want to…HaHa). You certainly put a new spin on a topic that’s been written about for a long time. Wonderful stuff, just great!ReplyCancel

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