For Example, using the statistics, if Asdrubael Vect charges a unit of 10 marines, what is his chance of killing them. 7 Attacks on the charge with preferred enemy, means he is hitting an average of 88.89% 5.5 marines die. Now yesterday I killed 3 out of a 6 man unit, which shows a 3.35% chance of happening. Rare indeed.
The above single shot lascannon has the following against a rhino/razorback transport. 14.8% chance of destroying it
Anyhow, check it out if you have not already and add it to your list of tools.
Heresy Combat Calculator