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The piston head in your AEG uses the forward motion of the piston to compress air and propel a BB down the barrel. There are multiple different kinds that each offer something different, from quieter operation to more consistent air seal and in this FAQ we’ll try to answer any questions that you may have.

Why does my piston head have an O-ring?

O-rings are the holy-grail of creating an air seal. Without an O-ring your piston head won’t be able to compress air very well, if at all.

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Why does my piston head have holes in it (porting)?

The holes on the face of your piston head allow air to flow behind the O-ring and push harder against the walls of the cylinder. This creates a much tighter, more consistent air seal.

Why is there a bearing in my piston head?The bearing on a piston head a premium, optional extra and the absence of one is not a problem. One end of your AEG’s spring sits on this bearing and allows your spring to rotate freely. Under compression and expansion the coils in your AEG spring make it want to rotate and the bearing allows this to happen freely, resulting in smoother operation and less stress on internals.

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Is a plastic or metal piston head better?

As your piston head moves back and forth rapidly, it requires less energy to move the lighter it is. Lighter materials are generally weaker, however, so both plastic and metal pistons have their pros and cons. A metal piston head is generally stronger and puts more stress on the gearbox, it may also be louder.

A plastic piston head is generally quieter, less durable but puts less stress on the overall gearbox.

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What is ‘Air Seal’?

The piston head compressed air on in the cylinder. Without effectively sealing that air in, it can escape and result in lowered and inconsistent FPS. This is what is referred to when we say ‘air seal’ and your piston head plays a large part in how consistent it is, along with your cylinder head and air nozzle.

A consistent and quality air seal is achieved with a well lubricated and good condition o-ring that perfectly contours to the inside of the cylinder.

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Can I use a metal piston head with a plastic piston?/Can I use a plastic piston head with a metal piston?

There is absolutely no reason why you can not use a plastic piston with a metal piston head or visa versa, aside from standard compatibility restraints that would occur regardless of material.

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Will a new piston head increase my FPS, Range, Rate of Fire or Trigger Response?

A new piston will not increase your airsoft gun’s range, it may increase your FPS however.A new piston head has the ability to increase your FPS by improving your airseal giving a potentially greater and more consistent muzzle velocity. Your AEG’s Rate of Fire (RoF) and Trigger Response will be affected by the weight of your piston and piston head. If your new piston head is lighter than the old one, you will notice a marginally faster Rate of Fire and Trigger Response.

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Will any piston head work in my AEG?

The majority of piston heads will work with the majority of AEGS, but there are a few things that you need to be aware of. Some AEGs may have a ‘bore up’ cylinder installed. This is a wider than standard cylinder that can hold more more. You will need to use a ‘bore up’ piston head for this, otherwise you will have a terrible air-seal. Some piston heads use ‘silent’ design that looks like a cone on the impact face of the piston head. This kind of piston head requires a a cylinder head with a similar shape to be effective.

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My piston head is broken, can I just glue it back together?

You have to bear in mind that your piston head moves at a great speed and slams forward with some considerable force. It’s highly unlikely that a glued together piston head would be as effective as a new one and there’s a good chance that it may break inside your AEG and cause damage to other parts.

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What is AOE?


AOE stands for ‘Angle of Engagement’ and is the angle at which the first sector gear tooth engages with the first piston tooth. The majority of guns from the factory do not have a correct engagement angle set, putting undue stress on the gearbox, piston and gears.

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