It has come to our attention that many AEG owners out there don't know the corner stones of AEG care! Although Marui has started printing its manuals in English, it still does not emphasize some of the most important things you must watch out for. So without further delay, we'll address some of the key points here. Nevertheless it is advisable to always read the manual. Even if it is in a language you don't understand, the pictures tell more than a thousand words!
Don't recycle BBs
Number one rule: Don't use shot BBs again, no matter how good they look. BBs may deform when fired out of an AEG - and will definitely deform and sometimes chip and crack when colliding with targets. Using BBs that are not completely round or that have chips and cracks may rip the hop-up rubber seal and damage the hop-up mechanism, or even get stuck into the barrel and cause severe damage to the gearbox! BBs that you pick up off the ground may also be coated with a thin layer of dirt - which again may scratch the hop-up seal and barrel.
Cleaning the Barrel
One of the most common factors leading to the loss of range and accuracy comes from dust and dirt buildup within the inner barrel. Once dirt builds up, it interferes and slows down the BB as it travels through the barrel, leaving you with less power and horrible accuracy. Also the lubricant from the cylinder may find its way into the barrel when a newly maintained AEG is operated, so cleaning the barrel is important even if you weren't shooting in a dirty environment. Cleaning is a must if you play a lot and doing so takes only a couple of minutes. Marui includes a cleaning rod with each of its AEGs. If you don't have one and use a rod made for real rifles (5.56mm) instead, make sure it's one piece to prevent scratching the barrel, and don't use any real gun solvents or brushes.
First you need to stick a piece of cotton into the "needle eye" of the cleaning rod, spray some silicon onto the piece of cotton, and then push it gently down the barrel. The most important thing to do before cleaning the barrel is adjusting the hop-up to minimum setting. If you leave the hop-up on and you try to force the cotton ball down the barrel right into the hop-up assembly, it may damage the hop up mechanism. After cleaning the barrel with a silicone patch, take a dry cleaning patch and repeat. If necessary, continue cleaning the barrel with clean dry patches until they come out as clean and dry as on the way in.
When maintaining Airsoft guns, don't use any mineral solvents such as WD40 or real gun oil. As good as they are for squeaky hinges, they will attack the rubber seals and ABS plastic parts of Airsoft guns and actually damage them. Only use silicone oil made for plastic and rubber parts. Using a thin weight silicone oil (10W-30W RC car shock oil for example) will provide smoother operation of the moving parts.
The manual illustrates the lubrication points to some extent, but generally you should spray some silicon onto moving parts and also into the BB feeding tube (the part where your magazine meets the gun...or, where the BBs are fed up into the hop-up unit. Doing this periodically will ensure you don't get BB jams at critical moments. Be sure to wipe off excess silicone, or you will quickly end up with a dirty gun.
Do note that excess use of silicone will attract dirt, and get where the oil is not supposed to be (electronics). The barrel of an airsoft gun is most accurate when it's as dry as possible. In the feeding tube clean surfaces are more important than a gallon of silicone: If the BBs jam because of dirt, silicone won't fix that problem.
In the heat of play and vibration from shooting the AEG, some screws may become loose. If you don't tighten them, you may end up with lost parts after you return from a game. Critical screws to check for include those that hold the front sights and muzzle (especially so on the MP5 and G3 series AEGs), the screw that fastens the selector switch (again common on the MP5 and G3 series), and screws on the grip butt-plate.
It's also a good idea to ensure any screw you can find on the gun is firmly screwed in (although don't screw them in too hard, or you may strip them). We're told by our customers that the front sight retainer screw on the MP5 A4 / A5 comes loose easily, as does the large screws that hold the M4A1 upper receiver handle to the lower receiver. As a rule of thumb, any screw which meets a metal thread is prone to loosening, if it's not secured with thread locking agent and/or a spring washer.
The motor in AEGs is precisely positioned so that it mates correctly with the gearbox gears. The way this is tuned is done by adjusting the hex nut on the bottom of your grip butt-plate. You will notice that there is a dab of red wax-like material on the nut - this was applied by Marui at the factory to prevent the screw from unwinding itself. Some models have a nylon disk on the inside to secure the screw. If in the unlucky event that this hex screw becomes loose and unwinds itself, the motor will shift downwards within the grip and come away from the gears. If this problem becomes severe enough, then you may find yourself with a stripped pinion and damage the bevel gear.
We would recommend you don't tamper with this screw unless you are sure that it has come loose. Visual inspection may help identify this, but the best way is by listening to the motor. To a trained ear, it is very easy to tell - a shifted motor will often allow much more play in the gears and your shots might sound much more hollow and the motor takes longer to wind up and get a shot off.
Should the need to adjust arise, it is advisable to make small adjustments (1/8 turn between shots). When the motor becomes too tight, the firing rate drops. Back out a bit and the position should be fine. In some cases the top face of the pinion may collide with the anti reversal steps on the bevel gear. You can tell this when the sound becomes clearly louder as you tighten the motor.
If the gear sound gets even louder when you tighten the motor, but loosening does not help either, the bevel gear needs to be shimmed again. It is most advisable to leave this to a professional.
To sum it up, normally don't tamper with the hex screw, and especially if you don't fully understand what it does. Over 99% of AEGs go through their life without ever needing this operation. If you have a modified AEG or if you have disassembled the grip butt-plate at some point in time, then this may apply to you.
Decompress the spring after each game and before storing
This is the most basic rule that everyone should follow. Due to the design of AEGs, it is important that you shoot your AEG in semi-auto mode for about 2 to 3 shots before storing it. Doing this will ensure that the spring is full decompressed! If you simply walk off a battlefield after much full-auto fire, and then store the gun for the days - chances are that your spring is in a partially or fully compressed state. Springs that are held in their compressed state for an extended amount of time loose their strength and you'll get a decrease in power the next time you use your AEG.
Note to TM PSG-1 and G&G L85 owners - this method does not apply to you. The default position for the spring in these models is in a compressed state - meaning every time you pull the trigger, it releases the spring from the compressed state, fires off the shot, and recompresses the spring - ready for the next shot. That's why there is NO delay when you pull the trigger. To decompress the spring for storage, refer to the manual which describes the little spring decompressing lever next to the trigger. In the L85 the lever is located inside the magazine well.
Follow these basic rules and your AEG will last you a long time. Hope this short column clears up some of the confusion!