http://www.youtube.com/watch?v=Si2zhgi7j2s[/youtube]
The rocket at 1:45 seems to be the HE rocket (weights at around 815 kg). The first one is a cluster rocket. Each launcher system fires 12 rockets. So maybe a strike of 12-24 rockets should suffice. These are actually quite large and powerful rockets, but I'm guessing that the bulk of the rocket's 815 lbs is made up of propellant (these have a range of 90 km!).
To indicate the differences between a BM30 Smerch strike and a Normal PR Arty Strike I drew some pictures with my amazing Paint skills.
Here's a standard artillery strike:

Here's a BM-30 Smerch (Hypothesized) strike:

(Note that I did NOT count out how many explosions there were relative to shells/rockets fired, this is just a scatter plot).
Notice that the BM30 strike is more linear and forms a more rectangular area than the artillery strike. This is because the rockets are fired in a row, along the same vector from a single source. Artillery is just distributed around the place. The BM30 also has a very large size, so the explosion is a bit larger.


