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Spring Upgrades for Electric Airsoft Guns

Posted by Matthew Meraz on 3rd Jul 2022

Spring Upgrades for Electric Airsoft Guns

Hello reader and welcome back to our blog! Today we are going to talk about upgrade springs in AEGs. Our tech tip series is designed to teach you more about the inner workings of your airsoft guns and equipment. We will show you how to maintain your guns as well as the upgrade potential.

AEGsutilize a spring inside the gearbox to push a piston inside a cylinder. The cylinder is a chamber where the air sits just before being forced out by the piston. 

The air that is pushed out is what drives the BB out of your gun and the more air pressure there is behind it, the higher the velocity of the BB coming out of your gun. With the installation of a different spring you can achieve higher or lower velocity depending on the spring you put in. 

Some airsoft guns as they come from the factory might shoot harder than what your local field will allow, so it may be necessary to put in a weaker spring inside. Sometimes you would want better performance out of your gun, so a spring upgrade might be in order to achieve the desired performance.

ASG springs come color-coded for easy identification

ASG Ultimate AEG Springs

How are airsoft springs rated?

Typically, springs will have a rating that looks like Mxxx. The M signifies meters and the number behind the M will denote the meters per second. Since the sport originated in Asia, they will use the metric system to measure and of course, we Americans who love to do things our own way will measure in Empirical measurements. So to get what performance you should expect out of the spring, convert that number in meters and to feet and you'll get a rough idea. 

An M100 spring = 100m/s = 300f/s or 300fps and this is stated as being measured with a .20 gram BB. This is not exact because different lengths of guns will get more out of certain upgrades due to the cylinder and barrel length and the potential volume of air. I have found that in most cases, these springs are underrated for their number rating and you can expect 30 to 50 more fps in many cases. You will have some manufacturers who rate their springs by a percentage number, such as 150%. This is rare to see but is often confusing. So here's a quick and dirty reference for springs:

M90 = 300-330fps

M100 = 330-360fps

M110 = 360-390fps

M120 = 380-410 fps

You can learn more about what FPS means here

I think the original manufacturer's intent was to mean that it is 150% of the velocity compared to an OEM spring, but by whose standards are they using to measure the OEM performance? Either way, if you see a rating that is outside the norm of meters per second, the results will be hard to gauge.

Modify springs are the most consistent, we have found

Modify Irregular Pitch Springs

Also as we as an industry move to chronographing guns in Joules, you'll have to use some judgment on your part to determine what FPS you have to be within when measured on a different weight BB, and then tune your gun based on the older style of measurement.

Irregular Pitch vs. conventional coil springs

Beyond ratings, there are different types of springs that can be had. Conventional springs have the same coil pitch all the way through the entire length of the spring. Irregular pitch springs have varying degrees of coil pitch throughout the length of the spring. 

The conventional spring produces the same force no matter where the piston is starting from in the shot cycle. Irregular pitch springs have varying degrees of tension throughout the spring making it easier on the motor to cycle no matter where the piston starts from. If the piston is almost fully compressed back and you attempt to shoot your AEG, a conventional spring would require more torque and battery power to pull the spring back, therefore creating more work/strain on the motor. 

Overall spring length could also lower your rate of fire a tiny bit. We have found that in our testing. When installing an irregular pitch spring, the side with more coils at the end should go on the spring guide side. The side with fewer coils goes to the piston side.

The difficulty of working on your own airsoft guns

I will classify airsoft tech work into a couple of categories which will help you decide what you want to attempt yourself and what you should go to an expert for based on your comfort and experience level.

When upgrading your springs, why not upgrade your piston while you are at it?

ASG Ultimate Polycarbonate Piston


  • Minor - this procedure could be done by anybody and you should do this yourself. As always, make sure you have a clear understanding and don't force anything or you could cause damage.
  • Moderate - this may require some minor disassembly. If you are not remotely technically inclined, you might want to seek help regarding this, otherwise, you may damage your equipment or cause it to function improperly.
  • Major - this requires detailed knowledge for disassembly and should be done by someone experienced. You could likely cause damage and ruin your equipment if you attempt.

It should be noted that in this day and age of Youtube and information everywhere on the internet, a lot of inexperienced people attempted something in the major category. We implore you to not do that (but you probably won't listen). Many times we will have a person come in with a fully disassembled airsoft gun that they were not competent enough to work on so we have to explain that the time we put into fixing that gun has doubled (which makes the cost of labor double).

Why? Because now we have to assemble a gun from scratch just go get it together, see what is wrong with the gun, then disassemble and work on the gun again to work on the problem that the owner originally tried to address. There also might be the issue of parts being missing so that makes the job take longer while people search their bedroom for an elusive spring or screw that may have got dropped during the process. Then there is the likelihood of damage to components incurred by people forcing parts in or trying to operate the gun in its incorrectly assembled state. Okay did that scare you away yet?

Well, regardless of my warnings, you have to start somewhere and build up your skills. I'd say if you have a spare broken gun to turn into a project, that's a good way to start learning. Don't do it on your brand new gun that someone bought for you with their money! You'll be sitting out and not playing as a result! Let's move on.

SHS Pistons

Let's classify what types of activities you can do with your airsoft guns.

Cleaning - Minor
The main thing you will be doing to clean your gun is just to clean the inner barrel and lubricate the bucking in your hopup chamber. This can be done on your own AEG or gas pistol.

Upgrade Your Barrel - Moderate to advanced
Swapping the barrel will entail you field strip your gun to access the barrel and hopup system. You will either install it into your existing chamber or have a full hopup setup ready to go which you need to put together. Overall it is not the most difficult job in it of itself but some guns are difficult to disassemble to get your hopup and barrel out. For example, an M4 style is going to be a moderate job. On an AK pattern gun, the front end and possibly gearbox have to be removed to get to the barrel assembly.

Doing something in the gearbox - advanced
This will more than likely require you to take apart the externals of your airsoft gun to reach the gearbox. After that, the gearbox is its own beast. The gearbox is assembled with carefully checked tolerances so if you put it together wrong, you can cause a lot of damage or make your gun perform worse. Critical components that have to be carefully installed and checked are the gears and the piston. Parts are not always drop in either. Due to the fact that manufacturing tolerances vary from manufacturer to manufacturer plus the difference in specs between gun brands for the same style of gun, this adds a lot of variables.

Quick-change Spring - Moderate
With a gearbox that has this feature, working on a gun is essentially halved. You might still have to take the gearbox out of the gun body, but you can change the spring without opening the gearbox and you could easily reverse it if the gun is not optimized to run the spring you put in there.

Quick-change Spring for ICS gearboxes - Minor
Sometimes spending a little more up front pays off! The ICS split gearbox means you open your M4 like a real AR and you can access the spring within seconds. You do not have to remove the gearbox out of the gun to do it!

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