Ok. Just remember Pepperpunch has also contact vector, so gas mask alone won't help them.
Suppressive fire will take the whole round but is probably the best solution to keep the guards from firing and kill the drones at the same time (What are the barricades made of? APDS will probably penetrate their cover too)
Suppressive Fire:
17d6t5 6 [17d6t5=3, 6, 3, 6, 1, 1, 3, 6, 1, 3, 2, 6, 6, 6, 1, 4, 1]
so -6 to everyone's actions and an EDG+REA roll to avoid being hit for the drones (which likely means no chance to avoid)