Originally Posted by dutchydoc
The smoke was more than likely vapor from the sudden expansion of the gas charge.
Agreed. CO2 or propane grenades often appear to have some smoke. It will be the vapor plus a bit of silicone oil exiting just like a GBB.
Also, less likely the smoke you saw, but the BB's from a larger nade like a madbull king will look like a giant cloud coming at you
Powder shots in the xmpb4 are less than dramatic.