[Izzleydill]

If a blast marker lands on an artillery unit how do you resolve it? Is it one hit? Is it one hit per model? And if its one hit per model do you still role to see whether it hits the artillery piece or the crew?

 

[Vaz]

Exactly as you'd resolve it against any other target.

 

[don_mondo]

One hit per model, total number of hits then randomized as normal.

 

[Winterous]

One hit per model, total number of hits then randomized as normal.

This.
You figure out how many hits, then you roll a D6 for each of them; 1-4 it hits a gun, 5-6 it hits a creman.
So it's possible for them all to hit crew, or guns, and none of the other.