What is an AEG (Automatic Electric Gun)?

What is an AEG (Automatic Electric Gun)?

As the name suggests, an AEG is an automatic gun powered by electricity.

What makes an AEG worth buying?

Airsoft guns are designed to be as realistic as possible, both in looks and operation. AEGs unfortunately fall down on the second point. While they do look like real firearms from the outside, the inside is totally different and shares more in common with a radio controlled car than a gun.

However, the AEG offers some real benefits, despite its lack of realism in operation...

Reliability
AEGs are reliable. They can shoot hundreds of BBs without getting hot, getting dirty or jamming.
Accuracy
While the accuracy of Airsoft guns (or anything that shoots a BB) is questionable at best, AEGs offer better consistency than most other airsoft replicas.
High capacity for ammunition
Most, if not all AEGs are available with High Capacity Magazines. These are magazines that hold several hundred shots instead of the usual 50. This means that the user can fire more shots without having to reload regularly. Excellent for skirmishing, especially outdoors.
Strength
AEGs are built around a central metal Mechbox that houses the gears, piston, trigger, etc... This makes the AEGs mechanical internals rugged and reliable, even when exposed to the stresses and strains of a skirmish environment. External strength varies from AEG to AEG, some being very fragile replicas, others being tough as nails.
Cost effective
Cost per shot is very low when using AEGs. The only power required to shoot the gun is electricity, provided by a rechargeable battery pack. These packs can be recharged thousands of times for very little money and offer thousands of shots per battery. There is no need to purchase gas or disposable batteries for these models. AEGs are however amongst the more expensive airsoft replicas that can be purchased.
Upgradeable
The vast majority of AEGs can be upgraded. This can include power/accuracy upgrades, add-on accessories and custom modifications. The AEG is versatile and cheap to upgrade or repair, as and when necessary.

How does an AEG work?

The diagram below shows the 'guts' of an AEG. This is the inside of the Mechbox in all its glory, with all its components still in place.

Figure 1 - The AEG Mechbox

A: Spring Guide	E: Cylinder Head	I¹: Sector Gear
B: Spring	F: Air Nozzle	I²: Spur Gear
C: Piston	G: Tappet Plate	I³: Bevel Gear
D: Cylinder	H: Trigger Switch	J: Non-Return Latch

In the cutaway diagram above, parts A through to F are responsible for the shooting of the BB. Parts G through to J are part of the reloading mechanism. When it is all working together, this is what happens...

The trigger is pulled by the shooter, which closes an electrical switch (H).
A Ni-Cad or Ni-MH battery pack (similar to those found in Radio Controlled Cars) powers a small motor (located beneath the Mechbox and meshing with the bevel gear (I³)).
The motor turns the bevel gear anti-clockwise, which in turn causes the other two gears to rotate - the spur gear clockwise (I²), the sector gear anti-clockwise (I¹).
As the sector gear turns, its visible teeth mesh with the rack on the underside of the piston (C), pulling it back. This compresses the spring (B) and stores the energy required for the shot. At the same time, the small white circular notch (the cam), offset on the face of the sector gear, connects with the rear-section (the tappet) of the tappet plate (G). This pulls the tappet plate and the connected air nozzle (F) backward about a centimetre, allowing a BB to enter the barrel.
As the piston is drawn all the way back, the tappet plate is released, pushing the BB forward into the breech (the BB's starting point in the barrel).
As the sector gear continues to turn, it will run out of teeth that can hold on to the rack on the under-side of the piston. As this happens, the piston is released.
As the piston flies forward under the pressure of the spring (B), it compresses a column of air in the cylinder (D). This air is squeezed through the air nozzle, in to the barrel, propelling the BB forward.
If semi-automatic fire has been selected, the sector gear activates an electrical cut-off as it returns to its starting position. This stops the cycle where it started ready for the next shot. If fully-automatic fire has been selected, this cut-off simply does not engage, allowing this cycle to be repeated over and over until the trigger is released.
Important Note: If shooting in fully-automatic mode, power to the circuit is cut as soon as you remove the trigger. Remember that the internal mechanism could be in any position at this point and the parts could be under considerable strain imposed by the spring. It is recommended that users shoot two semi-automatic shots to make sure the gun is reset correctly, before storing your AEG.

Throughout all of this, the non-return latch (J) stops the mechanism from moving backward. As mentioned above, when using fully-automatic mode, the moment you let go of the trigger could be at any stage during this cyclic process. If the spring is compressed at that moment, it will try and push the piston forward and the rest of the mechanism backward. This could be disastrous for the tappet plate (G).

If the cam pushes the tappet from below, as would happen if the mechanism were operating in reverse, the tappet is likely to snap off, as there is no opportunity for the mechanism to absorb this pressure. This would render the AEG unusable as no BBs would be taken from the magazine while shooting. Replacing the tappet plate is cheap, but not very easy, so this latch is a very important bit of kit to have inside the Mechbox.

How good is it really?

Replica realism (look) :	Very good, but varies. Size and shape are all right, although the really observant may notice many AEGs are slightly wider than the real-steel guns they are attempting to replicate. Some furniture can seem bulkier, thinner, thicker or in other way, slightly different, but you really have to know your stuff to notice. Trademarks are usually good, but can vary. Serial numbers where present usually reflect the fact that these are toys (e.g. "911COP" or "CQB999", etc...).
Replica realism (feel) :	Poor. Weight is usually much lighter than the original weapons, and the plastic bodies rarely do any replica real justice (creaky from lack of strength, light-weight, plastic feel). Metal bodied AEGs are normally much stronger and have a more realistic weight, but these are more expensive.
Replica realism (operation) :	Poor. Operational noise sounds more like an angry sewing-machine than a gun (whirring of gears/motor, delay before shot is fired)
General build quality :	Good. Reliability is very good on average and there is little that will go wrong with a stock AEG.
Cost effective?	Yes, if you use it a lot. Can be expensive, but widely acknowledged to be worth the price.
Upgradeable?	Yes. The AEG can almost always benefit from a wide variety of after-market parts. These can increase the power, the rate of fire and the appearance of the gun. Most upgrades can be done by the user, especially if they have a bit of experience taking things apart. There are guides on this site that show you how to take standard AEG components apart.
Target shooting suitability :	Very good. Comparative long range accuracy and consistent shots make the AEG a good target shooting gun.
Skirmish suitability :	Excellent! This is where the AEG really comes in to its own. If you skirmish without an AEG, you are likely to be at a disadvantage. High capacity ammunition availability coupled with the reliability and long range accuracy, this is a MUST for the serious skirmisher. AEGs are commonly hired out for use on skirmish sites and is the accepted standard for a good day's play.
Target audience :	Those that skirmish or want to target shoot regularly and replica collectors. Not specifically recommended as your first airsoft gun due to the price, but if money is no object, you won't be disappointed.