Technical Info from FAS part 2

[kuya jhas]

SHIMMING GUIDE: taken from wajoegween
AEG: Shimming
1) Preparation - Remove everything from the mechbox that will get in the way of getting to the gears. This includes the spring/piston/cylinder assembly, and then it depends on the gear box. With version two mechboxes, the little safety lever needs to be removed so that the selector plate can be slide forward and off. Now there should be only the trigger assembly left in place. With other versions, other parts may or may not need to be removed. When checking shimming, do not install the anti-reversal latch, motor or anything else that may restrict the gears movements in either forwards or backwards.
2) Shims and Bushings
[note: I speak only of Systema shims. I am not familiar with stock or other shims. For simplicity, I always replace all shims with Systema ones.]
There are three different sizes of shims, 0.5mm, 0.3mm, and 0.2mm thickness. There are two different diameters of shims, the small and the large. Of the two smaller diameter shims, they are noticeably different in thickness. They are the .2mm and .5mm thick shims. The large diameter shims are the .3mm thick ones. Since your reading this guide, your are most likely replacing the bushings. If the replacements are solid metal they will be a tight fit. I first try pressuring them into place by pushing with my thumb really hard. If it does not pop into place, I take something soft and tap it into place. Most commonly I end up lightly hammering them in using the plastic handle of a screw driver. Make sure to force the bushings into place EVENLY! If you are replacing the stock bushings with bearing bushings, they will be a loose fit, and it is easier to put them on the gears than to try to make them stay in place on the mechbox. Don't worry about how unstable the bearings feel, they will be plenty beefy when the mechbox is together.
3) Spur Gear
On the bottom(left) side of the gear, place a single .3mm shim. With the Fa-Mas, it might be necessary to have more shims than any other mechbox. With my only Fa-Mas shimming experience, I had to use two .3mm shims on that side, and generally a lot of shims all around. Put the gear into its place, and put the top(right) half of the mechbox on, and just hold them together tightly with your hands. Push the axle with a tooth pick or something similar, and note about how much it moves. Now it's just a game of guess and check with shims on the top(right) part of the spur gear. Once you think you have it just right, with little to no movement, put in three or four screws to make sure its held tightly(more than your hand can do). It should have very little or no movement side to side, AND you should be able to reach a finger in through the empty cylinder hole and freely spin the gear. If there is too many shims on the upper axle part, it will have resistance or be completely stuck. If there are too few shims, it will turn freely but have too much side to side movement.
4) Bevel Gear
Start with the bottom(left) half of the mechbox including the shimmed spur gear. Place two .2mm shims on the bottom(left) part of the axle and put it in its place in the bottom(left) half of the mechbox. Check for clearance between the teeth of the spur gear that mesh with the normal teeth of the bevel gear and the notched part that the anti reversal latch rides on.* If they interfere with each other, then the bevel gear needs more shims on the bottom(left). If there is ample clearance (unlikely), you may want to drop it down to a single .3mm shim. The idea here is: You do not want to compromise the gears' teeth because of the bevel gear having too many bottom(left) shims leading to minimal gear tooth surface contact between gears, but at the same time you don't want the anti-reversal latch contact area to be grinding with the spur gear. OK, enough rambling. Throw the right side on and check for movement the same way you did for the spur gear. Then guess and check, put in a few screws and do the final spin check with the two gears. Re-adjust and re-test as needed.
5) Sector Gear
Almost exactly like the bevel gear, start with the bottom(left) half of the mechbox including the shimmed spur gear and bevel gear. Place one .2mm shim and one .5mm shim on the bottom(left) part of the axle. Check for clearance.* This time you want to make sure the large diameter part of the spur gear is not going to be binding with the teeth on the sector gear that engage the spur gear on it's smaller diameter part.
*A general note about gear clearance: Remember that when the mechbox is together, the gears will not be able to twist(axels slightly off of parallel) relative to each other, so when checking the clearance, you may see interference that should not be there since you only have one half of the mechbox on. Make sure to not accidentally over shim the bottom(right) side of the bevel or sector gears because of this.
HOLY CRAP LOOK AT ALL THE INFO - JUST TO KILL A TANGO
*thank you to all those who contributed to the list! if you want to add to the reference, just reply to this thread


Upgrades:
After a while most players begin to think about upgrades and to improve their weapon. The first thought is probably to increase the muzzle velocity to gain extra range. But the only weapon that needs longer ranges is rifles like sniper rifles and the real important upgrades isn't to improve performance but to make the weapon more durable and to increase lifespan. Most players settle for only changing the battery to a bigger and to put in a slightly stronger spring. When an Airsoft weapon is upgraded to increase muzzle velocity the weapons lifespan will decrease. How powerful an Airsoft weapon is depends on three things. The strength of the spring that pushes the piston forward, the amount of air the piston compress and the precision of the barrel. When a weapon is highly upgraded it becomes a specialized tool for serious Airsoft skirmish and to dry-fire (i.e. without bullets) puts even more strain on the parts.

Spring:
There is two ways to measure how strong a spring is compared to a standard spring. There's the Percentage system and the Meter Per Second system. A standard AEG has a muzzle velocity of 90m/s (100%) with a 0.20g bullet. A M100 spring increases this velocity to 100m/s. The corresponding spring in the percentage system is 110%. There are M100, M110, M120, M130, M140, M150 and M160 springs. A very powerful spring requires that the entire gearbox be replaced.

Bearings & bushings:
The axles inside the gearbox is attached to the housing by small plastic bearings and these will eventually wear down. If these bearings are exchanged to metal or ball bearings, the lifespan of the mechbox will increase (almost double according to many players). Bushings are small thin plates that make sure that the gears in the gearbox are precisely aligned. These can be changed to "Accelerated" synthetic ones to reduce wear, although I personally trust the metal ones more than the accelerated.

Barrel:
The barrel in a standard Airsoft often has a internal diameter of 6.12mm. If this barrel is exchanged for a precision barrel with a 6.04 mm internal diameter the amount of air that slips by the bullet reduces and the benefits is that the bullet has less spread and about 5% extra velocity. The downside is that the barrel clogs up more often and has to be cleaned. A longer barrel increase range, but the barrel can't be too long since if the amount of air in the barrel is more than the amount of air the piston push forward, a vacuum will develop in the barrel and the bullet will be sucked back with a big speed reducement. There is a method called "Crater-cutting" that has the effect that just before the bullet leaves the barrel the air slips by and cuts a hole in the wall of air that is formed in front of the barrel. This isn't something for the common player and this is only used by the players that try to increase the range as much as possible.

Battery:
If a batteries voltage increase, so do the rounds per minute in an AEG motor. All standard AEG batteries has a voltage of 8.4Volts and the only difference between the different sizes is that a Large battery has a capacity of 1300mAh, while the other small standard batteries has capacity of 600mAh. This means that a large battery will last for about twice the amount of shots. Upgrades inside a gearbox often reduce the rate of fire and if you then use a battery with a higher voltage like 9.6V or 10.8V the rate of fire wont drop as much or even increase. A higher voltage also wears a motor down faster and more maintenance is required. It is possible to use 12V to power an AEG but this isn't to recommend since the wear is increase very much, the contacts in the trigger is faster worn out and the overall lifespan is sharply reduced. A battery with a higher capacity (more mAh), can be used under a longer time and can fire more shots. Upgraded weapons also require more current and the amount of shots that can be fired will decrease unless a bigger battery is used. The usual batteries are NiCd (Nickel Cadmium), but there is another type called NiMH (Nickel Metal Hybrid). The NiMH usually has a higher capacity (mAh), but they can't handle big currents very well and so they don't work well to most Airsoft weapons unless they're very big (about 3000-5000mAh). NiMH is more expensive and harder to charge and they shouldn't be fast charged.

When do you need to get a better battery? All AEG's either use the 8.4V 600 mah (Mini) or the 1300 mah (Large) in stock configurations. If you chose to upgrade an AEG's with a more powerful spring and gear set. The original batteries will not be sufficient for extended play. Your battery will drain faster due to the increased resistance of the heavier spring. For better performance and rate of fire, a 8.4V 2000 mah ( large type ) or 9.6V battery is highly recommended. For the AEG's that can only accommodate the mini type battery. The only option after gear box modifications is installing a 9.6V mini type battery for increased endurance or one can use an external battery. In some cases the 9.6V batteries may require slight modifications to your AEG in order to fit in the allotted battery space. We also have some special types of batteries for various types of AEG's these batteries come in special configurations that take into effect the space available inside your AEG. Some may also require modifications to your AEG, to fit correctly.

Gears:
The normal gears in a gearbox has an approximate lifespan of 30'000 shots, a new set of gears will last longer since they're made from better material. There is a set that increase rate of fire and reduce the motors power or reduce rate of fire but increase the motors power. The "Helical Cut Gears" is special gears that has a better grip between the gears and doesn't brake as easy as standard gears. The biggest supplier of upgrade and replacement parts i Systema.

Nozzle:
This is a small metal or plastic nozzle that transfers the air from the cylinder to the bullet. This is a cheap upgrade and the muzzle velocity increases slightly.

Motor:
Most upgrades reduce the rate of fire. By switching to a stronger motor the rate of fire isn't reduced as much. An upgraded AEG should have at least an EG700 motor. The strongest motor is EG1000. All new models that Tokyo Marui releases have EG1000 motors, but many of the older models have EG700 or even EG560. Not all AEG can have a motor upgrade. If the spring isn't replaced with a stronger than M120 the EG560 motor can take it, but the battery will probably has to be changed to a 9,6V or even 10.8V.

Piston:
A piston can be equipped with a "Silent" or "Anti-Vacuum" piston head. The silent piston head reduce the impact the piston makes in the cylinder and also reduce noise. The Anti Vacuum piston head prevents the forming of vacuum in the cylinder.

Mechbox:
This is a totally new mechbox with new and better gears, stronger spring, nozzle and other improvements. This isn't a cheap upgrade but the durability and lifespan increase and so do the muzzle velocity and overall performance. A new mechbox isn't available to all models, like the FAMAS doesn't have a upgraded mechbox. There are different versions of mechboxes since they're used in different weapon models. Version 1 is only used in FA MAS. Version 2 is the most common and is used in M16, G3 and the MP5s. Version 3 is used in AK47, MP5K & MP5K PDW and Sig SG55x. Version 4 is only used in the PSG-1 and is only semi automatic. Version 5 is used in the UZI and has the recoil system.

Metalbody:
This upgrade isn't cheap, but the durability and the damage resistance increase as well as the look of the weapon. The older models have often much cheaper bodies than the newer models.