FN P90 Hop-Up Maintenance & Service

The KRYTAC FN P90 uses its own rotary hop-up unit. It is easily accessible for maintenance.

Before performing any work on your P90, first remove the magazine and battery.

Accessing the Hop-Up Unit

To access the hop-up unit, you will need to separate the receiver from the stock.

Locate and press the receiver locking latch.


Slide the receiver forward and away from the stock.


Removing the Hop-Up Unit

Grip the hop-up unit, press it in, and rotate it 90° anticlockwise.


Pull the hop-up assembly out of the receiver. You will feel some resistance from the barrel o-ring before it is completely out of the receiver. Take care not to lose the hop-up spring, which will come out along with the hop-up unit and inner barrel.


Hop-Up Unit Disassembly

Rotate the hop-up rotary dial so that position 0 lines up with the indicator triangle.


Give the inner barrel a slight twist, which will disengage the lock on the barrel clip. You will see that the barrel clip is no longer flush with the hop-up unit. This makes the barrel clip easier to remove and will prevent damage to the barrel clip.


Now you can remove the barrel clip, allowing you to slide the barrel and hop-up bucking out of the hop-up unit.


If it's necessary to access the hop-up nub, slide the rotary dial off the hop-up unit, then use a 1/16" punch to remove the tension arm retaining pin. This will allow you to lift the tension arm out of the hop-up unit.


Hop-Up Unit Reassembly

When you are reassembling the hop-up unit, make sure that the inner barrel is oriented correctly. Match the notch on the barrel with the square locking tab on the underside. This is the same side that the hop-up position indicator triangle is located.


To confirm that you have installed the inner barrel correctly, after the barrel clip is installed, rotate the rotary dial to its maximum setting. Look through the hop-up unit and into the barrel. If the barrel is oriented correctly, you will see the fins from the hop-up bucking extending into the barrel. If not, repeat the above steps to remove the inner barrel, rotate it 180° and then reinstall.

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