Need *friendly* help...

You're going to need to ask a specific question.

Well, first off tell me what I need to know about electropneumatic markers....

There are so many types of eletro guns. Some of them consst of a poppet, spool valve, etc.

Its a spool valve, close to the DM/PM design, but with the bolt as one hard piece.

I would explain further, but I really wouldn't know how too. So here's a diagram

Ions are a solenoid driven, pneumatically operated dump-chamber/spool valve marker. As the diagram above shows, the marker uses air to move the bolt backward and forward by running air through a solenoid to push the bolt rearward creating a seal to allow a volume of air to build up in the dump-chamber. When the solenoid is then switched to an idle "vent" stage with the pull of the trigger, the opposing pressure built up in the dump chamber pushes the bolt mass forward breaking the seal and allowing the air to flow from the dump chamber, through the bolt, and to the ball in rapid succession while the forward movement of the bolt pushes the ball into the barrel and seals the breach at the same time. It's a simplified version of the shocker/matrix spool-valve set up which eliminates the need for a 3-way or 4-way solenoid to control the movement of the bolt since it uses the valve pressure to initiate the forward pulse which allows the air to escape the valve chamber. Earlier and more advanced spool-valve concepts use a solenoid to push the bolt rearward to seal the valve chamber and the same solenoid to push it forward achieving a higher rate of fire than you can attain using the system the ion does. This, of course, uses more air to achieve the same result which means that most of the older and more complex spool-valve systems are less efficient than single-phase bolt systems.