Angle of Engagement
Angle of Engagement, or AoE, is a modification for AEGs to adjust the angle at which the sector gear engages the piston. This is important for longevity of the piston, and especially important with higher performance electric guns.
AoE was first found 15 years ago by a man who calls himself Gungineer.
You will need a tool to remove material from the piston and you will need spacers to push the piston back. You have a few options for each.
For the removal tool, Dremels are best. These rotary tools remove material quickly and efficiently. When a dremel is unavailable, a simple file will do the job as well.
For spacers you have a few options. There are two different methods for the spacers. The first is piston spacers. These are spacers that sit between the piston and piston head. You can use many different materials, but nylon rings are the most common. The second method is using a spacer glued to the rear of the cylinder head. Sorbothane, or Sorbo, is the most common substance, but rubber washers are common as well.
To start with, you have to space the piston back so that the sector gear is engaging the piston face to face. Once you have this adjusted, you need to remove the teeth that interact with the piston.
Most will say to only adjust the AoE to allow for flat face contact, usually this means a roughly 11 O'Clock angle. Further experimentation suggests that a better angle is the 12 O'Clock position for the sector gear teeth. This seems to allow for pistons to survive more reliably in more extreme set ups.
 Star_folder tutorial via sqairsoft.com