The Co2 Magazine provides an energy of 1.2 Joule (360fps at 0.2g Bbs). The advantage of CO2 is that it works even at low temperatures. Also the high pressure makes the SSP-1 work very reliable.
The Gas Magazine provides an energy of 0,8 Joule (310fps at 0.2g Bbs). The smaller fps are great for smaller minimal engagement distances at CQB areas.
How to stack
Make sure the BBs are stacked properly to ensure reliable feeding of the SSP-1 magazines.