How to Adjust The FPS On Airsoft Gun? (Best Practices)

Lowering the fps on airsoft guns

Sometimes the less FPS is the more, especially when you need to lower it to fit the field limits, but increasing the FPS can be a plus outdoors. Having a powerful velocity airsoft gun can be a blast, but certainly it can put you in a weird situation when you realize that your favorite gun does not fit the field regulations and you can no longer use it.

Therefore you need to find a way to adjust that FPS and it can get tricky if the number of FPS you want to get rid of is not a small difference. Usually the airsoft fields tolerate up to 10 FPS over the limit, for anything else you will need to apply some changes to your gun that I will be sharing with you in this short guide.

In short, what seems to be the best way to deal with adjusting the FPS?

To adjust the fps on an airsoft gun you should prioritize changing or shortening the spring because it is where the velocity is generated the most. Other ways include wearing off your gun by continuous use or by simply getting a secondary gun.

Now, you might have heard that there are more ways to lower or increase the FPS on your gun, however most of other ways that people mention are not going to have a serious impact or might even destroy your precious replica.

Let’s get into a more detailed explanation why only severe ways work, why some are considered as cheating and should not be counted on and why some won’t have any impact and might hurt the gun furthermore.

Get a secondary airsoft gun

Before we get to the methods you can use to adjust the FPS, why would not you consider simply getting a secondary gun that you can use for CQB or whatever the purposes are and have the other one for skirmishes in the fields that allow higher FPS.

This is probably the simplest solution and with time you will anyways feel lured to add more guns into your collection as the time passes by.

So, if you make this in a smart way and upgrade your collection with functionality intent, you can have an SMG, shotgun , pistol and AEG, maybe sniper and cover all possibilities.

You never know where you going to end up when you join the airsoft community and to simply stick with one option that is suitable for one field does not always make sense.

Spring is the way to increase and lower the FPS

Till this day, I have only found this way to truly work for any major differences.

The spring is where the velocity is generated and although other parts like the Hop-up unit and barrel play role in how well the BB will keep the starting velocity before it reaches out of the gun, it should not be a major way to affect the FPS.

There are people who recommend shortening the spring by simply cutting it, but is it really a smart thing to do? I mean, if you do this you can not really go back and increase the FPS and sometimes you might want that FPS back.

This depends on what your needs are, whether you want to stick to that local field with certain FPS limit and completely adjust your gun to fit its criteria or perhaps, you like to change fields, travel a bit and use your airsoft gun in many other scenarios when the higher FPS may be beneficial.

FPS may not play a major role for range and accuracy and you do not need to exceed 400 FPS to have a great gun. Such gun will be fine in most fields, although sometimes additional FPS may help you with the range in some skirmishes where the field is built in such way that it appreciates extra range.

Therefore, I believe that the best solution is to buy a new spring that will offer lower velocity, open the gun and replace the old spring with the new one whenever you are about to play in a field with such FPS regulation.

Springs are not expensive and this is probably smarter than purchasing a whole brand new gun. You can find springs at price of $10 and something like M100 will probably do the job if you need to drop that FPS significantly.

However, this will require some basic knowledge with the replica’s inside parts, so bear in mind that if you do not feel confident in changing it yourself, lend it to someone who knows how to or learn to do it yourself, you might need that kind of self-mechanic skill later in life anyways.

Continuous use of a gun lowers the FPS

This is self explanatory to some degree, but people do not always pay attention to it. Whenever you operate a brand new gun with brand new inner parts, it will perform at its full potential.

With time some parts get worn out including the spring, piston head, cylinder and so on, as a reaction the FPS should drop down a bit.

This is not really a useful method because it takes long time and thousands of BBs shot in order to see any significant difference and even then it is not impactful if you need serious change.

However, knowing this can be useful because when you get that new gun, you can expect that its velocity will go down with time and you can make some plans in advance.

Use the duster gas

The previous part affected AEGs, however what is the case with GBBs?

One simple way to play with the FPS and to get it down a bit, is to use some less powerful energy source to power your gun at very first place.

Airsoft gas guns are greatly dependent on gas and this is the reason why you can often see major drops in performance on cold days and after the cartridge is almost empty.

Gas guns rely on gas source that much that the difference can be certain and huge.

Just think about why gas blowback guns often have worse velocity than gas non blowback guns. Gas powers everything in such guns and in case that it needs to power to sliding mechanism it is going to have less power to support the BBs.

Lower velocity batteries do not work

The previous thing may work for gas guns, however the AEG gearbox operates differently and although the electricity is also the energy source, it greatly differs with purpose from gas.

The gearbox on AEGs does not work this way and simply replacing a battery with a lower voltage one should not lead to any differences because the gearbox does not produce the velocity, but rather dictates the fire rate of a gun.

Heavier BBs are not really a choice

For a long time I thought that using heavier BBs is the way to drop that FPS and pass the chronograph, but it is not really a case in most fields.

Certainly when you put heavier BBs the FPS got to drop by a huge number, however it can be seen as cheating because the gun still has the same power and the weight of the BBs slow it down, but the power is still present.

You can pass the chronograph with this, but only if they allow it in the field and most often they do not and will demand that you test your gun with their BBs, which is often either 0.20 gram or 0.25 gram BBs.

I did not always pay attention to this because there are many airsoft fields in the world and many different rules, so some fields do not have any requirements at all and you are free to do whatever you want as long as you do not hurt players intentionally.

I mean, if you respect other players and use your high velocity gun that may have an FPS of 500, but only on certain distances and do not aim for the vulnerable body parts, it should be fine, after all you got your secondary gun that is often a pistol and it rarely has greater FPS of 350.

This depends from a field to field and there are many kinds of humans, sometimes you got to put the line that affects everyone because of a few rotten apples.

Velocity reducers do not work

There are velocity reducers on the market and perhaps you thought about getting one yourself in order to lower that FPS.

There are multiple issues with these little devices, so let me name a few.

Velocity reducers on airsoft guns do not work as intended at all times and sometimes when you switch from semi to auto it neutralizes its effectiveness and there are also players claiming that they might jam your gun.

Whether it all is true and how likely it is really to jam your gun, I simply do not know, but I know that they can be easily taken off airsoft replicas after they pass the chrono test, so often the fields do not allow them.

If everyone agrees that you can use this small device, then it perhaps could have some purpose, but it is likely not to be.

Other pointless options you should not try

I have heard many stories of people trying to lower the FPS by drilling holes in their inner barrels, messing up with the hop up unit, cutting the barrel in half or even purposely damaging O-rings and other important parts that have an impact on gun’s compression.

All these methods may have a small impact on your gun’s FPS, especially if you mess its compression, however is it really worth destroying your gun and thus affecting its accuracy and lifespan?

I would stay away from any of these methods unless you simply do not care and want to experiment.


The two best ways to get the job done are getting a new secondary gun or changing the spring, everything else pretty much is not worth your energy and time.

For gas guns there is also a gas substitute method worth a try, but most people use AEGs anyways.

After you have calculated how much FPS you need to drop, research the soft springs in the market and compare them to your current one, you will be able to lose those 50 FPS this way which is often the number that most players have an issue with.

If you have something powerful that reaches close or over 500 FPS, for instance a sniper, I think it is better to get a new gun without even messing with internals.

Also expect that your gun will lose some FPS with time as you wear it out, but do not count on big difference, it may lose only 10-20 FPS.


Dino is a thrill seeker who loves to share what he learns about his favorite hobbies.

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