- Common Faults
- Performance Metrics
- Performance Tuning Procedures
- Advanced Performance Systems
- Battery Terminology
- Rechargeable Battery Chemistries
- Rate of Fire (ROF)
- Muzzle Velocity (FPS)
- Muzzle Energy
- Trigger Response
- Minutes of Angle (MOA)
- Effective Range
- Motor Height
- Compression / Air Seal
- Angle of Engagement
- Short Stroking
- Swiss-Cheesing / Skeletonizing
- Electronic Trigger (MOSFET)
- Active Braking (AB)
- Burst Circuit
- Fire Controller / Fire Computer
- Resettable Fuse / PPTC Fuse / Polyfuse
- Double Sector Gear (DSG)
- Sorbothane (Sorbo)
- Air Brake
- Battery Cell
- Battery Pack
- Capacity (C / mAH)
- Voltage (V)
- Maximum Discharge Current (IMAX)
- Self Discharge
- Energy Density
- Specific Energy
- Memory Effect
- Voltage Sag
- Smart Charger
- Balance Charger
- Nickel Cadmium (NiCd)
- Nickel Metal Hydride (NiMH)
- Lithium Polymer (LiPo)
- Lithium Iron Phosphate (LiFe / LiFePO4)
- Acrylonitrile Butadiene Styrene (ABS)
- Polyamide (PA) / Nylon
- Polyacetal (POM) / Duracon / Delrin
- Polycarbonate (PC) / Lexan
- Acrylic (PMMA) / Plexiglas / Perspex / Lucite
- Potmetal / White Metal
- Bluing / Black Oxide
A short circuit is a condition where electrical current flows through an incorrect or unintended path, resulting in system malfunction. Short circuits can be prevented by maintaining the insulators on all wires and connectors in a gun. When they occur, short circuits are usually mitigated by the electrical fuse installed in the gun (if one is present). The fuse will allow the short circuit to continue for a short amount of time before ‘blowing’ and shutting off current to the system. Unchecked short circuits can be very dangerous as they will cause heating and potentially fire as they damage wires and electrical components throughout the gun. Electrical shock is usually not a danger with short circuits due to the low voltages that most airsoft guns operate at (8.4 to 12V). To diagnose a short circuit, look for the symptoms described above and use an electrical ‘multimeter’ with ‘continuity’ or ‘diode’ testing to identify any parts that may be electrically connected in error. To repair a short circuit, power must be shut off to the system, any breaks in electrical insulators repaired, and the fuse replaced if blown.
An open circuit is a condition where current does not flow due to a break in the electrical system. Open circuits can be prevented by careful handling of all wires and connectors in a gun. When an open circuit occurs, the gun will be completely unresponsive to trigger pulls. To diagnose an open circuit, check all electrical connectors in the gun (battery, motor, quick disconnects), check the gun’s fuse (if present), check all switches for proper operation and check the wiring for any breaks. An electrical ‘multimeter’ with ‘continuity’ or ‘diode’ testing can be useful to speed up this process. To properly repair an open circuit, repair or replace any damaged connectors, fuses, or switches. If a break in a wire is found, the wire may either be replaced or ‘soldered’ back together. Electrical tape is not a sufficient fix for a broken wire or connector.
A trigger jam is a condition where the trigger of an AEG does not properly act to fire the gun. In a trigger jam, the trigger may be immobile, or ineffective at closing the trigger switch. Due to the design of most AEGs, trigger jams can occur when firing in semi-auto due to a periodic misalignment of the semi-auto cutoff lever. Usually, all that is needed to clear the jam is to switch the gun’s firing mode to full-auto, fire a burst, then switch back into semi auto and resume firing. To avoid trigger jams, make sure that the trigger is held down for the entire cycle of the gearbox. Pulling the trigger too quickly while firing in semi-auto is the most common cause of trigger jams.
In some guns like designated marksman’s rifles that are modified for operating only in semi-auto, trigger jams are a significant problem as full auto is not available to clear the jam. Careful modification of the interface between the trigger switch and semi-auto cutoff lever and installation of an active braking system can lower the probability of trigger jam significantly. Sometimes a secondary trigger switch or trigger override can be installed that allows the user to bypass the jammed trigger to activate the electrical system and cause the gearbox to advance out of its jammed state.
A barrel jam is a condition where a BB or debris is stuck in the barrel, preventing passage of any further BBs and air from the gearbox. Prolonged firing while a barrel is jammed can be extremely detrimental to the internal parts of the gun’s gearbox due to phenomenon like pre-engagement. Pistons, air seal nozzles, and gear sets can all be damaged by firing while the barrel is jammed.
To prevent barrel jams, be sure to properly adjust your hop-up unit and properly lubricate and clean your barrel. The barrel can be cleaned using pure silicone oil, small sections of paper towels and the cleaning/un-jamming rod which was included with the gun.
To clear a barrel jam, completely turn ‘off’ the hop-up unit and use the unjamming rod to push the stuck BBs or debris back out of the gun’s BB feeding nozzle. In many cases, spraying a bit of silicone oil into the jammed area will make it easier to clear the jam. For stubborn jams, the barrel may need to be removed from the gun.
To prevent damage to your gun when a barrel jam occurs, stop firing immediately if you notice that the gun does not emit BBs and the gun makes a ‘softer’ than normal sound when the gun is fired (as opposed to the harsher than normal sound when the gun runs out of BBs).
A gearbox jam is a condition where a broken part, debris, or insufficient power supply prevents an AEG’s gearbox from cycling. A gearbox jam can be an indicator of a wide range of situations, from broken pistons and gear sets to just a weak or uncharged battery. When a gearbox jam occurs, the gearbox will not make the characteristic ‘whirr’ then ‘pop’ sounds which occur when the gearbox cycles. In most cases a low grinding noise or click will be heard when the trigger is pulled. If no sound is heard when the trigger is pulled, or if the trigger feels unusual, check for an open circuit or trigger jam instead.
When a gearbox jam does occur, first try to cycle the gun using a known good or more powerful power source. If the gearbox is still jammed, try lowering the motor height. If this has no effect, then the gearbox must be opened to diagnose the source of the gearbox jam.
Over-spin is the phenomenon that occurs in AEGs when excess momentum in the gun’s gears is able to at least partially compress the spring after the gun is fired in semi auto. In moderate cases, over-spin can cause inconsistent trigger response and cause extra wear on internal parts due to the extra tension from the partially compressed main spring. In extreme cases, the gun may fire 2 or more shots per trigger pull in semi-auto. Lighter gear sets, heavier main springs, lower voltage batteries and active braking systems can all reduce over-spin in AEGs.
Pre-engagement is a condition where the sector gear will re-engage the piston’s teeth before the piston has returned to its rest position. Pre-engagement can occur both when a barrel blockage prevents the escape of air and the full return of the piston, and when the gun is run at a high rate of fire with a relatively weak spring, where the spring is not strong enough to fully return the piston before the sector gear completes its cycle. By definition, pre-engagement implies that the sector gear will engage teeth forward of the pickup tooth, usually causing damage to these teeth or destruction of the piston. To reduce the possibility of pre-engagement, a stronger main spring can be installed, the piston and sector gear may be short stroked, or the battery voltage can be decreased.
Rate of fire is the measure of how many BBs a gun can fire in a specified period of time. Common units of measure for rate of fire are ‘rps’ (rounds per second) or ‘rpm’ (rounds per minute). Rate of fire can be increased by using more efficient motors, higher voltage batteries, high speed gear sets, and optimizing electrical and mechanical systems including proper shimming. Many players value higher rate of fire because they are able to fire more BBs at their target when firing in full auto, maximizing their probability of scoring a hit. Unfortunately, high rate of fire puts greater wear on many internal components due to the higher rate they must cycle at. Additionally, high ROF guns usually achieve higher round counts during their lifetime, leading to more overall wear on the gearbox.
Muzzle velocity is the measure of the speed or velocity of the BBs that a gun fires. Common units of measurement are ‘fps’ or ‘ft/s’ (feet per second) and ‘m/s’ (meters per second). Muzzle velocity can be increased by installing a more powerful main spring, improving the efficiency of the gearbox’s air compression and air seal, and by installing tight-bore barrels. Improvements in muzzle velocity can increase a gun’s effective range, increasing the distance at which players can successfully score hits. Unfortunately, improvements in muzzle velocity only improve effective range in a dimishing relationship as the forces of air resistance act more strongly on faster projectiles.
Muzzle energy is a measure of the amount of kinetic energy a BB carries as it leaves the gun’s muzzle. This is directly related to the gun’s muzzle velocity and the weight of the BB. The common unit of measurement is ‘J’ (Joules). Most guns produce fairly constant muzzle energy regardless of the weight of BB fired. The same gun will fire lighter BBs with greater muzzle velocity, and heavier BBs with lesser muzzle velocity, but both BBs will have similar muzzle energy. Muzzle energy indicates the amount of damage of gun will be able to do, and is usually the basis safety-oriented muzzle velocity and BB weight limits imposed by airsoft organizations and insurance companies. Minimum engagement distances are calculated by pro-rating the distance at which the BB will have slowed down to an acceptable energy level to comply with safety regulations.
Trigger response is the measure of the quickness of an AEG’s first shot after the trigger has been pulled. All AEGs experience at least some lag between trigger pull and firing the BB because the gear set must spin up and cycle the piston. Trigger response is considered especially important for AEGs which will be used mostly in semi-auto. Installation and use of high speed gears, high torque motors, lower powered springs, higher voltage batteries, and active braking systems improve trigger response.
Accuracy is the measure of the ability of a gun to fire BBs on the intended target. In general, most guns can have their sighting systems adjusted to make the gun ‘accurate’ even though the gun may be lacking in precision.
Precision is the measure of the amount of deviation in impact location between multiple shots fired at the same target. A gun able to place most of its shots very close to one another is considered precise. Precision is usually measured in Minutes of Angle or MOA.
To improve precision in an AEG, tightbore barrels and improved hop-up units, buckings and nubs can be installed. To maximize precision, one should make sure that the gun has an excellent air seal and low shot to shot deviation in muzzle velocity. Because deviations in muzzle velocity affect the amount of backspin the hop-up will impart to the BB, this greatly affects BB trajectory at the edge of the gun’s effective range.
In real firearms, 1 MOA or lower is considered very good precision for a rifle. Due to the poor ballistics of BBs and the lower power airsoft guns shoot with, airsoft MOA ratings are much higher.
Minutes of angle is an angular measurement usually applied to ballistics. One minute of angle, or MOA, is defined as 1 inch on the target at a range of 100 yards.
- 1 inch at 100 yards: 1 MOA
- 1 inch at 50 yards: 2 MOA
- 3 inches at 200yards: 1.5 MOA
Effective range is the distance at which a gun can reliably place shots on target. Shots taken at distances further than a gun’s effective range cannot be expected to hit the target. In airsoft only the most powerful and precise guns have an effective range exceeding 300 feet. Most guns have an effective range closer to 100 to 200 feet. Effective range is affected by the gun’s muzzle energy, precision, and the ambient conditions including temperature, elevation, humidity and wind.
Performance Tuning Procedures
Motor height refers to level of engagement of the motor’s pinion gear with the bevel gear in the gearbox. Proper motor height is necessary to minimize noise and maximize performance and durability. When motor height is too ‘high’, the pinion and bevel gears are too close to one another and the gun may make a grinding noise while cycling or be unable to cycle. When motor height is too low, the pinion and bevel gears are too far from one another or are unable to make contact. The gun may sound harsh while cycling, be unable to cycle while producing a buzzing noise, or fail to cycle while making a high pitched whine. The motor height adjustment screw, usually found at the base of the gun’s pistol grip, must be tightened or loosened to adjust engagement. This screw may be anything from a tiny 1.5mm hex set screw to a large, threaded and slotted plug. Tightening this screw raises motor height, loosening this screw lowers motor height. The proper motor height can usually be determined by adjusting this screw while listening to how the gun sounds when fired. The proper setting should make the gun’s cycling smooth as possible and maximize the gun’s rate of fire.
Shimming is a process of adjusting the engagement of the gears inside a gun’s gearbox. Proper shimming is necessary to maximize a gun’s rate of fire and durability. The key to shimming is ensuring that the gears teeth mesh with one another as completely as possible while ensuring that the gears faces do not contact one another or any part of the gearbox shell. Shimming is adjusted by installing thin metal washers, known as ‘shims’ of varying thickness on the axles of gears. It is considered good practice to remove as much side to side play along the gear’s axles as possible while ensuring that the gears are still able to spin freely.
Compression or air seal is a qualitative measurement of the effectiveness of the AEG’s air seal components (piston head, cylinder, cylinder head, air seal nozzle & hop-up bucking) at retaining air when the piston is released. A good air seal depends on quality components and proper lubrication, and is key to maximizing the shot to shot precision of the gun’s muzzle velocity.
Angle of engagement is a term that refers to the initial meshing of the piston’s pickup teeth with the teeth of the sector gear. Because the sector gear’s teeth must approach the piston at an angle, in some cases the teeth can mis-mesh or interfere with one another.
Though it may seem counter-intuitive, the piston’s second tooth commonly interferes with the sector gear’s teeth reaching the piston’s first (aka “pickup”) tooth.
Common adjustments to AOE are removal of the second and partial removal of the third tooth on the piston as well as adding washers between the piston and piston head to move the rest position of the piston’s pickup tooth. Some manufacturers produce pistons with the second tooth already removed.
Short stroking is the practice of removing teeth from the piston and sector gear to decrease the amount of time for which these two parts stay meshed. The reasons for short stroking include increase of rate of fire and elimination of pre-engagement. Because short stroking reduces the distance over which the main spring is compressed, it decreases the load on the gearbox as well as decreases the air volume which the piston is able to compress. This results in a higher rate of fire but a lower muzzle velocity. One important consideration in short stroking is that the piston’s last (or “release”) tooth must be made of steel for wear resistance and durability. For this reason, pistons with multiple steel teeth on the release side of the rack are preferred because the unused teeth may be simply removed. Otherwise, the single steel release tooth must be extended by removing the teeth adjacent to it and moving it into the space created, which can be more intricate and time consuming to perform. When a piston and sector gear are short stroked, the same amount of teeth must be removed from both parts for proper operation. Piston teeth are always removed from the ‘release side’ and it is considered good practice to remove sector gear teeth from the ‘pickup side’, especially when many teeth are removed. Removing teeth from these locations ensures that timing of the piston’s release with the motion of the tappet plate stays consistent. This is usually a custom modification, but some manufacturers do produce pre-short stroked piston and sector gear combinations.
Skeletonizing is a process of removing superfluous material from a piston body to reduce its weight. The goal of skeletonizing is to both improve the performance of the piston and to increase the piston’s durability. A lighter piston puts less load on the gun’s gear set and motor which can improve rate of fire. A lighter piston reduces the severity of the impact impulse on the piston’s pickup tooth – a common cause of piston failure, and reduces the amount of shock transferred to the gearbox shell, improving durability. When skeletonizing a piston, it is common to remove material from the top of the piston body and the area between the piston’s rails and teeth. Care must be taken not to compromise the structural integrity of the piston. This is a custom modification only; no manufacturers currently produce pre-skeletonized pistons.
Advanced Performance Systems
A MOSFET or ‘Metal Oxide Semiconductor Field Effect Transistor’ is a small electronic device which is used to increase the efficiency and durability of a gun’s electrical system. Because a gun’s original trigger switch can degrade and erode due to the high currents they must control, a MOSFET is installed to handle the high current switching instead. MOSFETs are solid state devices with no moving parts, and thus no arcing and degradation occurs as it would with a physical switch. MOSFETs are wired into a gun’s original trigger system and do not change the external operation of the gun. MOSFETs have less electrical resistance than a gun’s original switch and can thus improve the gun’s rate of fire by allowing more power to reach the gun’s motor.
Active braking is a method that uses the gun’s motor to stop the gears after the shot has been completed or the trigger has been released. Active braking is primarily used to eliminate over-spin in high rate of fire guns and provide more consistent trigger response. Especially effective active brakes can eliminate the need for an anti-reversal latch in some gun setups. Most active braking systems are implemented in conjunction with an electronic trigger. The active brake is a secondary MOSFET that shorts the terminals of the motor when the trigger is released to create braking force.
A burst circuit is an electronic device which uses a MOSFET to activate a gun’s motor for a short period of time, allowing the gun to fire multiple times per trigger pull. A burst circuit is a primitive version of a fire controller, usually only using a timer to activate the MOSFET for a predetermined amount of time. Burst circuits are configured by using a small screwdriver to adjust the resistance of a potentiometer and thus set the time delay. Using different voltage batteries and discharged batteries can cause the burst circuit to become mis-configured, causing the gun to fire bursts with more or less shots than intended. Most fire controllers implement a burst feature and are usually much more accurate than a simple burst circuit.
A fire controller or fire computer is a computerized device that controls the firing of an AEG through the use of a programmable microcontroller and one or more MOSFETs. Fire controllers are the most advanced form of electronic systems used in AEGs. They can implement many features that were unheard of until several years ago including: shot completion, short circuit detection, low battery cutoff, rate of fire control, MOSFET overheating prevention, burst fire, empty magazine detection, and even simulated bolt & bolt release function. Fire controllers are usually configurable by the user in the field using trigger pulls or by activating different switches on the unit. Many fire controllers can even be re-programmed with new firmware that implements new or different features. Some fire controllers usually require the installation of extra sensors to enable functionality like empty magazine detection and simulated bolt function, but most only require an extra wire to be attached to the mechanical trigger switch.
A resettable fuse is an electronic device which is used as a replacement for a traditional single use fuse. Also known as a Polymeric Positive Temperature Coefficient (PPTC) Fuse, or by the brand name Polyfuse, these fuses are capable of regulating the amount of current that passes based on their temperature. When large amounts of current are drawn through a resettable fuse, it heats up, and after several seconds of sustained current, the fuse will greatly increase in resistance, limiting the amount of current drawn by the system. When the current is removed, the fuse will cool and return to its less resistive state, allowing the gun to function one again. In the case of a gearbox jam where the resettable fuse intervenes, the trigger need only be released to begin the resetting process. In the case of a short circuit where the trigger switch is not involved, the battery must be unplugged to allow the fuse to reset. In general, resettable fuses take longer to ‘blow’ than a fast-blow single use fuse of the same amperage rating.
A double sector gear is a special type of sector gear which features two sets of piston teeth and two tappet plate nubs. As opposed to a traditional sector gear which completes one cycle of the piston per revolution a double sector gear, as its name implies, completes two cycles of the piston per revolution. Double sector gears are primarily used to increase a gun’s rate of fire. These are considered specialist parts and require significant preparation, knowledge, and effort to make function properly. Because a DSG must have two sets of teeth as well as sufficient spacing between these sets to allow the piston to return, double sector gears are by definition short stroked.
Sorbothane is a brand name for a viscoelastic urethane polymer which is used for its vibration and shock absorption properties. In airsoft, Sorbothane is usually used in AEG gearboxes to absorb the shock of the piston’s impact with the cylinder head, and to prolong the life of gearbox shells. Sorbothane cylinder head and piston head pads are designed and sold to airsofters for this specific purpose, but the material can be used anywhere where high shock occurs which may affect reliability over time, such as in airsoft gas-blowback systems.
An air brake is a specially designed cylinder head and piston head set that create a cushion of air which slows down the piston at the end of its stroke. The purpose of an air brake is to reduce the severity of the piston’s impact with the cylinder head and thus gearbox shell, helping to extend the life of these components. Typically an air brake takes the form of a small protrusion from the front of the piston head which mates and seals with a matching depression in the cylinder head as the piston returns to its forward position. These surfaces seal the cylinder head’s nozzle and do not allow all of the air to escape from the cylinder. This trapped air acts as a cushion between the piston and cylinder. When implementing an air brake, one must be sure not to make the brake too efficient, or the piston will not be able to return to its forward position in time for the next cycle of the gearbox, resulting in pre-engagement.
A battery cell, also known as an electrochemical cell, is an energy storage device and is the basic unit of a battery pack. A cell has a nominal, or normal, voltage, capacity, and maximum discharge current which are characteristic of its design and chemistry. Cells are most commonly connected in series to create a battery pack with a higher voltage but the same capacity as a single cell. It is also possible to create a battery pack by connecting cells in parallel, increasing the pack’s capacity, but retaining the voltage of a single cell. A cell’s capacity varies with its physical size but its voltage does not.
A battery pack is a collection of electrochemical cells which is used to store energy. All batteries have a capacity, voltage, and maximum discharge current depending on the type and orientation of the cells they were assembled with.
Capacity is the maximum amount of charge which a battery cell is capable of holding, and is usually referred to, simply, as ‘C’. Capacity is commonly measured in miliamp hours (mAH). Capacity is proportional to the amount of shots that an AEG can make on a single charge of the battery. In general, an AEG will drain the battery by 1/2 to 1 mAH for each shot it makes, depending on the efficiency of the gun and battery.
Voltage is a measure of the amount of electrical potential a battery cell or battery pack produces. Voltage is measured in volts (V). Most battery packs used to power AEGs are in the 7.4 to 12V range. In an AEG, increases in battery voltage will cause the motor to spin more quickly, resulting in a higher rate of fire.
Maximum discharge current is the measure of the maximum amount of current a battery can provide to a circuit. The maximum discharge current of a battery varies depending on the number and type of cells used. Batteries with higher maximum discharge current are capable of running AEGs at a higher rate of fire when compared with a battery with the same voltage but lower maximum discharge current. Because batteries with higher max discharge current experience less voltage sag, they provide the gun’s motor with a higher effective voltage while the gun is running.
While maximum discharge current is not commonly specified for NiCd and NiMH battery packs, all LiPo and LiFe packs give a ‘C rating’, which allows one to calculate the max discharge current for that pack. Simply multiply C, the battery’s capacity, by the C rating, and the result is the battery’s max discharge current.
7.4V 1200mAH 20C LiPo Battery
C Rating = 20
Imax = 1200 x 20 = 24000mA = 24A
Self discharge refers to the phenomenon where most rechargeable batteries will slowly lose their charge over a period of months. The self-discharge rate of a battery is the measurement of the percentage of the battery’s capacity which it will lose in the period of a month. Self discharge rates range from 30%/month for NiMH cells to 5%/month for LiPo and LiFe cells.
Energy density is the measure of how much charge a battery holds in a given volume. Common units are mega-joules per liter (MJ/L). A battery with greater energy density can hold more charge in a smaller volume. As battery technology progresses, the energy density of batteries increases.
Specific energy is the measure of how much charge a battery holds in a given weight Common units are joules per kilogram (J/Kg). A battery with greater specific can hold more charge in a lesser mass. As battery technology progresses, the specific energy of batteries increases.
Memory effect is a term which refers to the tendency of certain types of batteries to lose capacity when re-charged before being fully discharged. NiCd cells in particular experience significant memory effect, and thus should be fully discharged before re-charging to maintain peak capacity.
Voltage sag is the reduction in the voltage a cell or battery pack produces when current is drawn from it. Voltage sag is caused by the internal resistance of the cell and the maximum rate at which the chemical reaction can create electrical energy. Voltage sag is particularly noticeable when batteries are run near their maximum discharge current, which many airsoft guns are capable of drawing. Higher quality and higher capacity batteries tend to experience less voltage sag and can thus provide more power.
Smart charger is the general term for any charger which includes extra control circuitry to avoid over-charging batteries. Because over-charging can degrade and destroy most batteries, a smart charger should be standard equipment for all airsofters. Some smart chargers are programmable, with different charge currents, charging threshold values, trickle charge, and even discharge features.
Most smart chargers intended for use with NiCd and NiMH cells use a negative delta peak (-?peak) method to detect when these batteries have completed charging. When these cells reach full charge, their voltage will drop very slightly. The smart charger looks for this drop and when it occurs, the charger stops supplying current to the battery.
Smart chargers should not be used for lithium (L-ION, LiPo, or LiFe) cells unless they are specifically designed to be. As lithium cells don’t have a negative delta peak when they complete charging, the smart charger will continue charging them until they are destroyed which can result in fire and explosion.
A balance charger is a device which charges all the cells in a battery pack to the same voltage. Most balance chargers are intended for use with lithium cell batteries where exact control of cell voltage is important to avoid damaging the cells. All balance chargers have a connector for the balance connector of a suitable battery and may have a standard, high current, battery connector to allow for faster charging. Balance chargers intended for LiPo and LiFe cells have built in voltage cutoffs to avoid over-charging the batteries which could result in damage to the cells, or fire and explosion. Some smart chargers may integrate balance charging into their feature-set.
Rechargeable Battery Chemistries
Nickel cadmium cells were some of the first used in airsoft. Because of the superiority of NiMH cells, few airsofters still use NiCd battery packs. These cells have a nominal voltage of 1.2V. NiCd cells are usually connected in a series of 7 or 8 to form packs of 8.4 to 9.6V. The advantages of NiCd cells are their lower cost, higher max discharge current, lower self-discharge rate, and ease of charging. The disadvantages of NiCd cells are their low capacity, low energy density, and tendency to experience memory effect. Because they contain toxic cadmium, special care must be taken when disposing of NiCd cells.
Nickel metal hydride cells were introduced as a drastic improvement to the performance of NiCd cells. NiMH cells are the de-facto standard for battery packs in airsoft. These cells have a nominal voltage of 1.2V and are usually connected in a series of 7 or 10 to form packs of 8.4 to 12.0V. The advantages of NiMH cells are their much greater capacity, ease of charging, lack of memory effect, and many voltage options. The disadvantages of NiMH cells are their higher cost, lower max discharge current, lower performance in cold conditions, and higher self-discharge rate.
Lithium Polymer cells are a relatively new technology but are now coming into use in airsoft. LiPo cells have a nominal voltage of 3.7V and are usually connected in a series of 2 to 3 to form packs of 7.4 to 11.1V. These packs can be connected in parallel to increase pack capacity. The advantages of LiPo cells are their greater capacity, high energy density, high max discharge current, good performance in cold conditions, low self-discharge rate, and lack of memory. The disadvantages of LiPo Cells are their requirement of balance charging, limited charge rate, fewer voltage options, and the necessity to closely monitor the cells to avoid damage.
Lithium Iron Phosphate cells are an emerging technology and were introduced as an improvement to the performance and safety of LiPo cells. LiFe cells have a nominal voltage of 3.3V and are usually connected in a series of 2 to 4 to form packs of 6.6 to 13.2V. These packs can be connected in parallel to increase pack capacity. The advantages of LiFe cells are their greater capacity, high energy density, higher charge rates, high max discharge current, good performance in cold conditions, low self-discharge rate, lack of memory, and increased safety over LiPo cells. The disadvantages of LiPo Cells are their requirement of balance charging, fewer voltage options, and the necessity to closely monitor the cells to avoid damage.
Composites are engineered materials created from two or more source materials. They are designed to incorporate the best properties of each material to create a product which is superior to both source materials. The most common composites in airsoft are combinations of a polymer and glass fiber. These are often called fiber reinforced polymer or FRP. FRP is commonly found in gun bodies and pistons. The glass fiber increases the stiffness, durability and wear resistance of the material.
ABS is one of the most commonly used polymers in airsoft. Because of its low cost, high strength, toughness, and impact resistance, it is commonly used for gun bodies on cheaper airsoft replicas. Though it is a useful polymer, it isn’t preferred in airsoft because it tends to become shiny with handling and can cause creaking sounds at joints in the material when it is flexed. It is sometimes used in composites with glass fibers which improve its appearance and strength.
Nylon is a polymer commonly used in airsoft. It can be found in pistons, piston heads, spring guides, tappet plates, and gear bushings as well as gun bodies. It is a highly resilient material with good abrasion resistance, high strength and resistance to chemicals. Nylon is sometimes found as part of a composite with glass fibers, called Fiber Reinforced Nylon or FRN.
Polyacetal is a polymer often used in high quality internal upgrade parts for AEGs. It can be found in pistons, piston heads, tappet plates, and air seal nozzles. It is more rigid than nylon and has a relatively slick surface, reducing the need for lubrication. It is highly chemical resitant but has a lower impact strength than other polymers. Thanks to its high hardness, it can be machined into very precise shapes and sometimes used in place of metal parts.
Polycarbonate is a polymer often used for impact resistant lenses in protective eyeware, and internal parts for AEGs. It is extremely durable and highly impact resistant, but with low scratch resistance. Polycarbonate is commonly seen in pistons and tappet plates, as well as a component in glass reinforced composites. As a protective lens, polycarbonate is superior to acrylic because of its greater durability and impact resistance.
Acrylic is a polymer infrequently seen in airsoft products because of its inferior properties when compared to polycarbonate. Many airsofters attempt to construct clear, bb resistant shields using acrylic, only to find that the material is relatively easily shattered by BB impacts.
Aluminum is an elemental metal which is commonly used for high strength / low weight parts in airsoft. It is found in many different grades which indicate its quality and strength. Aluminum is commonly found in gun bodies, pistons, piston heads, cylinder heads, air seal nozzles and spring guides.
Titanium is an elemental metal which is used for high strength / extremely low weight parts. Titanium is rarely found in airsoft guns due to its high cost but can be found in some pistons.
Potmetal is an alloy of multiple lightweight metals such as aluminum, magnesium, and zinc which is very commonly found in airsoft parts, especially gun bodies and gearbox shells. Pot metal is used for its low cost and ease of casting. Since there is no standard for pot metal, different concentrations of source metals and finishing techniques mean its properties can vary widely. Most pot metal tends to be relatively brittle, however. Steel and aluminum are considered much more desirable materials than pot metal.
Steel is an alloy of iron and carbon that is used to create extremely high strength parts. Steel is commonly used for flash hiders, some gun body parts, gears, bushings & bearings, main springs, anti-reversal latches, cylinders, cylinder heads, piston teeth, pins and screws. Because it is harder to cast and machine, steel is only used where is is necessary to keep the gun from failing prematurely.
Anodization is a finish which is applied to aluminum, titanium, magnesium and zinc in an electrochemical process. It is a relatively durable finish which is more resistant to wear and abrasion than paint. Though most anodization in airsoft is black as it is primarily used on parts for gun bodies, anodization can be found in nearly any color. Anodization is grouped into three categories, Type I, Type II, and Type III, depending on the chemical process used and the finish thickness. Type I is the thinnest and least durable coating while Type III is the thickest and most durable. Type II and Type III anodizations have a porous surface and can be dyed to the desired color.
Bluing is a controlled oxidization finish which is applied to steel using an electrochemical process. Blued parts coated with oil resist rusting better than uncoated steel. Generally, thinner, shiny blued finishes are called ‘Bluing’ while thicker, rougher finishes are referred to as ‘Black Oxide’, although the chemical process is the same. Most steel parts in airsoft have a black oxide finish.
Parkerization is a protective finish which is applied to steel and zing using an electrochemical process. It is considered to be more effective than bluing at preventing rust formation on steel parts. Parkerization is rarely found on airsoft parts, but is commonly used for the guns that many airsoft replicas are based on.
Neodymium is a rare earth metal which is a very powerful permanent magnet. Neodymium magnets are commonly used in high performance airsoft motors as they allow the motor to produce much more torque than a traditional ferrite / ceramic magnet.