[Drakker]

The Action Army parts are cheap for a reason. They're okayish, but not the best. I am not impressed by their cylinder and piston. While I never used their hop-up unit, feedback has that they require some work, you will definitely need a new nub, and it has all the drawbacks of the PDI chamber without any of the advantages. It's a crappy one part design where you have to push the barrel and rubber inside like AEGs which makes precise adjustments to the angle of the hop-up rubber pretty much impossible, and you don't even have left-right adjustment available like the PDI chamber to compensate. You will also have to remove the mag and fiddle with an Allen wrench every time you want to adjust your hop-up, which gets old really fast and is why I ditched the PDI chamber in the first place. You should definitely stick the the TM chamber, just get and upgraded hop-up arm and shim it correctly and it will work marvel, and you will get none of that BB side-hooking people are complaining about with the stock chamber and heavy BBs, which is the only "advantage" of the AA chamber.

If you do end up buying the Action Army cylinder, you will need a large diameter piston, like the Laylax or the Action (just "Action", not action army, yeah, confusing) piston. Smaller pistons like the PDI and King Arms will just leak like crazy. Stay away from the action army piston, its a terrible design with glued o-rings as shock dampeners and it has no air brake and its impossible to fit one in.