According to Prime Mechanics Airsoft this BCM Air MCMR 11.5 AEG Build With Helical Gears sounds like an HPA airsoft rifle. This build is equipped with an Aimpoint T2 Hollywarrior, Surefire M600, and Surefire SOCOM RC2 suppressor (Dytac). Other parts are a Gate Titan II Bluetooth, Begadi Mamba motor 28 tpa + Lonex Helical pinion, SHS 12:1 DSG, Lonex Helical (spiral) bevel gear, and MagicPad️. It has a power of 1.1J with 0.28g.

Another Airsoft Tech 101 lesson as part of the "Inside The Gearbox" series by The Airsoft Tech. Going inside the gearbox, he talks about Helical Gears and they do especially for high-torque AEG gearboxes. There are different sellers of Helical Gears so just be more discerning in choosing sets for your AEG.