How do I use the on-board gun in GTA Online (XBox)?

How do I get the on-board gun of the Insurgent or the Speedo?

I can drive the car but I can't get the gun.

Neither on the cross pad nor when I press Y for a long time.

You can only do this by holding down "Y".

Try to stand at the back door and hold "Y" there.

Unfortunately, this does not work🤷♂️

I still get in the front.

As a passenger, I can't throw people out of my car when I press Y Lange.