Conclusions

Piston weight vs Rate of Fire vs Muzzle Velocity
The trends established in Part I of the Mega-Piston Review continues, as the heaviest Systema Aluminum Piston also resulted in the lowest measured rate of fire. Muzzle velocity variances remain within average standard deviation, as is to be expected given previous results. The addtion of piston geometry into the mix may have some correlation with measured muzzle velocity, but more tests are needed before a definitive relation can be stated.

Piston Durability
The results clearly indicate that all 3 pistons have no trouble handling an M140 spring. The ICS and Systema pistons, being aluminum, exhibted some edge deformation of the first tooth due to impact with the sector gear while the Deepfire piston displayed little to no deformation thanks to the use of a harder metal for its teeth. The Deepfire piston clearly has the best combination of strength, weight, and shock absorbing capability given its nylon body, and should be strongly considered for low rate-of-fire/semi-auto, high power applications such as an "AEG sniper", with the necessary caveat that it will likely also cause the most sector gear wear. Systema's Aluminum Piston with its teflon coating is a good alternative to the Deepfire piston should sector gear wear be more of a concern. Because its aluminum construction is softer than the typical steel used in aftermarket gearsets, the relative rate of wear is more favorable than the Deepfire piston. The addition of teflon coating to the piston body and teeth should also help to reduce wear. ICS' aluminum piston, while lighter than Systema, lacks the benefit of Systema's teflon coating and finishes last in this roundup.

What Now?

All three pistons performed exceptionally under the testing conditions, and it is evident that a more stressful testing platform is necessary to separate these pistons. As such, subsequent tests of these pistons will be conducted using an M150 spring. The inherent brittleness of harder materials such as aluminum can theoretically lead to sudden and catastrophic failures given sufficient stresses and it is my hope that this will eventually occur given more testing cycles.