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Guide: Upgrading Range, Accuracy and FPS

Posted: Thu Feb 05, 2009 1:52 pm
by Moondog
Guide: Upgrading Range, accuracy and fps
by Moondog

Everybody wants an greater range and accuracy in their weapons. The facts are these:

Accuracy is mostly determined by the quality and weight of your BB (heaver is more accurate). Mass effects inertia, and inertia is the resistance of an object to change velocity or direction. This means heavier BB's are less effected by cross-winds than lighter BB's and will follow a straighter path to the target. Weight + velocity = accuracy.

Accuracy is also effected by the consistency hop-up system which imparts back-spin on your BB. A defective hop-up or dirt in the barrel can cause a BB to spin off-center and curve right or left of center.

Range is determined by the air pressure your gearbox generates (or gas) and weight of the BB and the quality of your hop-up. Air pressure can be measured in exit velocity of the BB in feet-per-second (FPS). Essentially: More FPS equals range. But this 'raw' range can be further enhanced by adding back-spin lift to the BB (hop-up) and using smooth, heavier BB's.

Increasing FPS is the most common reason for people to open their gearbox (other than repair). In AEG's your spring determines your FPS. Other modifications and upgrades may be required to allow you to use the upgrade spring reliably. The motor merely compresses the spring. It's the release of the spring which drives the piston in into the cylinder and compresses the air through the nozzle and barrel which sends your BB flying.

To increase FPS you can do any of the following:
• Add a tightbore barrel 6.04mm (or smaller)=5-10FPS
• Fix leaks=5-30FPS
• Upgrade spring=50-200FPS
• Longer barrel=~2-4FPS per additional inch
• Bore up Kit=~5-10FPS

With any of these upgrades, your actual results will vary. Everybody's AEG is slightly different. So putting the exact same spring in one guys M4 will yield different results than another guys M4 or another guys G36. So take these FPS numbers with a grain of salt.


Fix Leaks
This may seem like a no-brainer and mundane task but it's often the hardest to accomplish. Also, if you have a major air leak, it can wipe out any benefits from other upgrades. Leaks occur in many points in your gearbox such as the piston o-ring, cylindar o-rings, nozzle, hop-up unit, or hop-up bucking. Be sure when you're working on your gearbox that you inspect the quality of all those seals.

Simply replacing your piston O-rings when they're worn can improve your FPS by 20%. And you can buy a variety pack of good quality plumbing O-rings from any hardware store for less than $5.
A loose bushing can be fixed with a little plumbers teflon tape.


Tightbore Upgrade
Replacing your stock inner barrel (typically 6.08mm wide) with a tightbore (typically 6.04-6.01mm wide) increases your FPS because it reduces the space between your BB (which is actually less than 6mm wide) and the inside of the barrel. Less space, means more air is stuck behind the BB pushing it forward out the barrel.


Upgrading your Spring
This is the most common means of drastically increasing your FPS. Your gun's FPS is almost entirely governed by the strength/hardness/elasticity of your spring. The spring pushes the piston in to the cylinder, compressing the air which pushes your BB through the barrel and out the gun. Your motor simply compress the spring.

The maximum strength spring you can put into your gearbox depends entirely on the parts which make up the gearbox. In a stock Tokyo Marui gearbox, the hardest spring you would want to put in is a Systema M110/PDI-150. The stock motor and gears in a TM would have a difficult time with a M120/PDI-170 spring (or may not be able to compress it at all.) For most players a gun that fires from 300-350 fps is more than sufficient for most airsoft games.

Systema springs are more common but PDI springs are softer and gentler to the gearbox. All springs 'break in' after initial use and their FPS lower slightly. PDI springs are in a sense pre-broken in. Be advised that they are slightly thicker than Systema springs and may not fit with certain pistons.

Springs Needed for Approximate FPS
340-360fps you will need a M110/PDI-150 spring
370-390fps you will need a M120/PDI-190 spring
400-430fps you will need a M130/PDI-210 spring (this is ~400fps with .25g BB's)
430-460fps you will need a M140 spring*
460-500fps you will need a M150 spring*
*These are only allowed for use in semi-only rifles


Steel Gears, Bushings, Shims
With M120/PDI-170 or harder springs, you will be putting increased pressure and strain on your gears. Tokyo Marui (TM) and older clone gears are too soft and may strip or fail. This is why they need to replace with high strength steel gears and metal bushings. Newer vintage clones (since 2007) come with upgraded steel gears pre-installed.

Bushings are the circular bearings that fit your gears to your gearbox walls. Shims are washer-like spacers that let you micro-adjust the height of each gear relative to each other. You will need to shim these new gears properly or you risk stripping them or causing friction which damange them and will rob you of FPS, battery life and rate of fire (ROF).


Hi-Torque Motors
Unless you have an ICS, KWA or other pre-upgraded AEG's, you will likely need to buy a high-torque motor such as those made by Systema, Hammer, Guarder. As motors age, they lose strength and torque. Stronger motors are generally more efficient but the harder strain of an upgrade spring also means that you'll be using up your battery faster.


Torque Up Gearsets
If you don't want to replace your motor (or your spring is so strong that even an upgrade motor isn't enough), a Torque-up gearset functions like a car's transmission, changing the gear teeth ratio to increase torque output by lowering your ROF (slightly).


9.6v and LiPo batteries
Actually it is the amperage that effects torque not the voltage but finding out your battery's amp output is problematic. Suffice it say, large batteries output more amps than mini-batteries. But you may need a 9.6v battery to give the motor a bit more juice to pull a PDI-190 spring and to compensate for a lower ROF. Your stock gearbox should be able to handle this without any problem but lower quality clones often have cheaper quality wiring. In worse cases you will need to replace the wiring in your AEG or bypass the fuse.


Spring Guide
With a harder spring you will also need a metal spring guide, ideally with a bearing. The spring guide is a peg that holds your spring in place within the gearbox. The bearing on the spring guide and inside the piston allows the spring to rotate freely as it compresses and decompresses.


Piston/Pistonhead
Higher strength springs put more pressure on the piston and pistonhead. You'll want to buy a reinforced piston that with teeth that will resist stripping (some come with metal teeth or partial metal teeth). You'll also want to buy a reinforced pistonhead that can withstand the repeated harder impact.

Some choose metal heads but reinforced polycarbonate pistonheads and pistons are more than durable enough for 400fps springs and have the added benefit of being lighter, less draining on your battery and quieter when firing.


Longer Barrels
The longer your inner barrel, the longer your BB is under pressure and the higher your potential FPS. But the increase in FPS is relative (about 2-4fps per extra inch in extended length). The exact numbers a little sketchy because when folks install longer barrels they tend to be tightbores too. If you are installing an inner barrel that is longer than 509mm long you may want to install a bore-up cylinder set to offset the larger volume of air in the barrel.


Bore Up Cylinder Kit
The more air you have pushing the BB, the faster it will go. A bore up has a larger diameter air nozzle and thus you need to replace your cylinder head, piston and pistonhead. But this performance increase is negligible with short barreled AEG's (those under 300mm long) and AEG's with sub 400fps springs. This is the least cost-effective FPS improvement.


LPEGs and Early Clones
Some low price clone AEG's (LPEGs) have very low quality internal parts. Upgrading them is ill advised as the parts are weak and break under the strain of a +350fps spring. Do not put an upgrade spring in a cheap AEG's plastic gearbox. It will not last past a couple of shots, if at all.


The new baseline: 360fps
Originally airsoft guns were made for the Asian market with 300fps limits (>1 Joule.) Since 2006, to appeal to the US market, most Clone AEG's have been pre-upgraded with M110 class or stronger springs and have reinforced internals to handle them. Since 2008, it's become common to see AEG's shooting +400fps out of the box. So in some cases you may not need to modify your AEG at all.


Final Words of Advice
Upgrading your AEG is the Dark Side of the Force. It is very alluring and sexy and a seemingly easy path to more kills. Upgraded AEG's require more maintenance, are less reliable and more prone to catastrophic breakages. Often to change one part you need to change 5 others. Once you go down the path of of the Dark Side, the costs increase exponentially.

Remember, it's not the FPS of the AEG but the quality of the player that gets kills. And may the Force be with you.

Re: Guide: Upgrading Range, Accuracy and FPS

Posted: Wed Feb 25, 2009 3:55 pm
by whogben
I hope this isn't the wrong place for this, but if you're interested in increased *effective* range your rate of fire is as important as your FPS.

FPS increases your maximum range, but your maximum range is well past your effective range - definitions vary but my definition of effective range is the distance at which you have an 80% chance of hitting a standing target in a 2 second burst of fire.

A high FPS rifle trades rate of fire for maximum range, but by decreasing rate of fire you decrease the number of BBs in those 2 seconds and may actually decrease effective range. A quick example:

You have a KWA M4 firing 380 at 25 rounds per second. Maximum range is 180 feet, and each bb has a 5% chance to hit at 150 feet..

You can add high torque gears to this and an M150 spring to make this setup shoot 500 but the rate of fire will decrease, say to 10 rounds per second. Maximum range is 250 feet. Using the heavier BBs the new high FPS bbs each have a 7% chance to hit at 150 feet.

In 2 seconds of fire the lower FPS M4 outputs 50 bbs with 50 * 5% chances to hit, averaging 2.5 hits.

In the same two seconds of fire the higher FPS M4 outputs 20 bbs with 20 * 7% chances to hit, averaging 1.4 hits.

That said higher FPS does result in higher maximum range, it's impossible for the lower FPS M4 to hit at 250 feet while with enough fire from the 500 fps gun a bb will eventually hit -> but in practical skirmishing increasing your rate of fire extends your effective range towards your maximum range, and for most guns shooting at 400 fps, for most rifleman players, higher rate of fire will result in more kills at a game than higher fps.



Parts Choice Notes for Cheapest FPS Upgrades

350-400 FPS
First priority is a metal spring guide. Stock pistons&heads can usually survive 400 fps springs, but should be your next reliability upgrade. After that upgrade any plastic bushings to metal.

400-450 FPS
Stock gears & metal bushings can typically handle 450 fps, but stock motors & pistons typically cannot (exception: ICS motors). You should replace the spring-guide and piston&head, and then you have a choice: You can either add a high torque motor, or change the gears to a higher torque set - either one will work, but the motor is an easier beginner upgrade. If you fire a lot of rounds (10,000) or so stock trigger contacts have a good chance of burning out and for best reliability should be replaced.

450-500 FPS
You need to replace the gears with a high torque set, piston&head, spring-guide. If you will fire a large number of bbs you should replace the trigger contacts. The next most likely failure is the stock cylinder-head, which is a good reliability upgrade at this point.

500+ FPS
You need to replace the spring-guide, piston & head, cylinder-head and gears. As you put higher and higher springs in you will eventually need a high torque motor, with <600fps and infinite torque gears a TM EG700 can barely pull the spring. If you are using this gun fully automatic you should upgrade to a MOSFET and deans connectors. At FPS over 500 it is often a good idea to replace a V2 gearbox shell (M4, MP5, G3).