How to Make an Airsoft gun Shoot Slower Permanently

How To Make An Airsoft Gun Shoot Slower Permanently

Airsoft is really fun, especially when all players are playing fairly. One of the unfair and dangerous things you can do on the airsoft field is when you do not stay within the FPS limits of the particular field you’re playing in.

You’ve probably seen a few videos where cheaters use a gun that was way too hot and almost injured another player. Different fields have different FPS limits and you might be wondering how to make your gun shoot slower.

Even with the proper gear, players can still get hurt so it’s important to follow the limitations of FPS. Let’s check out a few things you can do to slow down your gun.

FPS Restrictions

  1. CQB – Average CQB arenas will require that you have a 300 maximum FPS when you are using full auto and 350 maximum FPS in semi-auto.
  2. Outdoor Fields – requires you to shoot no faster than 400 FPS  for auto guns and no faster than 450 for semi-auto guns.

Below is a representation of the average FPS restrictions in Airsoft Fields

Field TypeAutomatic Guns FPS RestrictionSemi Automatic FPS Restriction
CQB Field300 FPS350 FPS
Outdoor Field400 FPS450 FPS

Now this restriction on FPS is based on 0.20g BBs.

The most important thing to consider when thinking about FPS limits is not necessarily the FPS but the amount of energy that the gun is shooting at.

This is referred to as Joules. Heavier BBs will shoot at different FPS but will have the same amount of Joules and this is the thing that most fields will be measuring for.

Over and above the restrictions within the field, shooting BBs with a high amount of energy, even if they are below the FPS, can injure an airsoft player. It’s therefore essential to be careful about the amount of energy coming out of your gun to make sure that you do not injure a player in your field.

1. Why is FPS Important?

BBs moving at higher speeds than what is generally allowed is likely to cause injury to an airsoft player. Some of the worst injuries would happen in places like the neck where most people don’t normally have protection. An airsoft BB can cause serious injury especially if it penetrates the skin in a delicate place.

While injury from an airsoft BB is unlikely if it is shot at normal speeds it becomes a different story if the limits are breached. This is why it’s really important to add FPS limits to control the game’s outcome and let players play safely.

Then there is the part where you would be called a cheater and hated in your airsoft field if your gun is shooting too hot.

2. When Do You Slow Down Your Gun

You would normally need to reduce the shooting speed of your airsoft gun in the following cases.

  1. When the gun modification you just did increase your FPS past the acceptable limits. You may have upgraded something in your gun that increases its FPS and you may now need to lower the rate to acceptable levels.
  2. When you’re playing CQB with a gun that was designed for outdoor play. CQB usually requires that your gun shoots at lower FPS. This is because the engagement is usually in close quarters than field play. This means that BBs shot from the same gun will hurt way more and could cause more injury in CQB than when shot out in the field.
  3. If the gun you purchased has a higher FPS than what is allowed on your field. Some guns shoot high FPS right off the box. You may need to do some modifications to reduce they’re shooting speed to acceptable levels.

Reducing Your Fps

Below are the different methods of reducing the FPS on your Airsoft Gun.

1. Replace the Spring With an M100 or M90 Spring 

This works by dismantling your airsoft gun gearbox and replacing the spring that is currently there with a weaker spring that will deliver less energy when it is fired.

An M100 or M90 spring is going to help reduce your FPS since it has had lower tensile strength than regular springs. Be sure to confirm if your gun will work with this spring before buying it.

The difference between the M100 and the M90 is the strength of the spring. The M100 shoots hotter than the M90 and you would choose one or the other depending on the amount of reduction to FPS you are looking for.

Ask The Pros

The gearbox to your airsoft gun is a sensitive part so before doing this, make sure you know what you’re doing. It is easy to mess up the gear configurations within your gun and this may make your gun start breaking gears and jamming up.

Get advice from an airsoft tech who knows how to effectively dismantle and reassemble airsoft guns. You may want to shim your gun as well. Shimming is done to improve the efficiency of the gears by fitting them tightly but far enough to avoid unnecessary friction between gears. 

2. Cut Your Gun’s Spring to Reduce the Fps

Other than buying an m100 or m90 spring, another option you try is cutting your spring to reduce its strength. The problem with this approach is that you are not guaranteed to reduce your FPS to the desired level with this method. It may either reduces too much or not reduces enough and you are not guaranteed to get the results you would expect.

The way to do this is the same as the method above but this time you will not have to buy the spring. In case you cut too much, it may be well just time to purchase a new spring and try the method above.

3. Use Heavier BBs

Shooting heavier BBs will cause your FPS to reduce since the force being produced will need to push a heavier BB which will cause its speed to be reduced.

The force applied on a BB will always be the same but the speed will reduce. Since many fields measure Joules together with FPS, this method may not work for you since the Joules of your gun may still be powerful enough to injure anyone.

Most fields also require using their provided ammo and it would only waste your newly bought BBs. Try checking with your local fields first before doing this method.

4. Break in Your Spring

It is common in anything we use regularly to wear and tear. So it’s only inevitable that your gun’s FPS will slow down eventually after a few hundred or thousand shots. 

The only problem with this method is that there is no actual number of shots that determine wear and tear. Each component is made differently and there’s no way of knowing which will wear down first. 

Also, there’s a case with wasting BBs. Unless you can find other local fields that allow your gun’s FPS, doing this method would mean shooting your guns outside the field, meaning outside of any official gameplay. 

5. Purchase a Different Gun

Guns have different FPS and it’s only obvious that some of these guns will have lower FPS. One of the most effective methods is just simply getting the appropriate gun for the field you want to play at. 

Airsoft guns can hurt and having these restrictions are really important. So checking with your local fields becomes necessary before purchasing a gun. You may have a high FPS gun but if you can’t use it in an official match, it may just well be for display or showing off to your friends.

How to Replace the Spring in Your Airsoft Gun

If you would like to change the spring yourself, you will need to understand how the internals of your airsoft gun work to ensure that you know your way around your gun before ever starting to dismantle it.

A good way to start is to find a video of how to dismantle your particular airsoft. Make sure that the video goes through all the steps in making you understand the parts and mechanisms of the gearbox.

Here’s a video of an M16 being taken down for a spring replacement you may want to check out. Since M4s and M16s are manufactured the same, you can use this to dismantle an M4 as well.

Some of the tools you will require are:

  1. Phillips Head Screwdriver
  2. Allen Key in the right size for the screws on your gun
  3. A flat head screwdriver
  4. Hammer in case you need to yank anything


Make sure that you know what you’re doing before heading down this method. Tinkering can be a fun and exciting activity to do with your airsoft guns but it can also mess up if you lack gun knowledge. Aside from lowering your gun’s FPS, you can make your guns louder as well.

Lowering your FPS to an acceptable level will help you protect the players out on the field and help avoid getting branded the jerk by other airsoft players. It’s also important to make sure that you stay safe and use the necessary safety precautions and gear to ensure that you and your fellow players don’t get any injuries.