As has been established in Part I of the Mega-Piston Review, increased piston weight equals increased inertia, and in a cyclic system such as the AEG mechbox, additional reciprocal moving mass will place addtional strain on the motor, thereby reducing the rate of fire. The full metal pistons clearly suffered from a reduced rate of fire compared to the polycarbonate pistons in the previous review as well as the nylon Deepfire piston. The distribution of muzzle velocity measurements among the different piston weights remains minimal, well within the average standard deviation of +/-2.62 fps for all samples as established previously.

The addition of piston geometry into the mix has turned up a possible interesting correlation. The piston with the largest "Full Rack Excursion" was the Systema Aluminum piston, and it correspondingly showed the highest FPS reading. The Deepfire and ICS pistons showed identical excursion numbers, yet the ICS still maintained a small FPS advantage. This result may seem contrary to the measurements, but upon further examination, the Deepfire piston also had the tightest inner piston bore. This fact can be clearly felt when inserting a spring into the Deepfire piston, as resistance to the spring is distinguishable. This fact may have introduced more friction to the equation, hence lowering the FPS measurements of the Deepfire piston and may have reduced the ROF measurements as well.