So you want to give the marines marksman scores on how they are performing at a shooting range?
There are rules for range penalties so I would let them make the rolls, a success gives 1 point, panicking substracts a point., the more points the marine has at the end of the target practice, the better his marksman rating.
This is along the lines of what I'm looking for. A quick day at the range to introduce the Players to the very basic idea of how to roll the dice and how Panic works without tossing them straight into the mouths of Xeno hell. No muss, no big deal, and no penalties for mistakes and/or bad rolls. Rather than just make it into a dice roll session, the Shooting Range is a way to do that as well as have the players get into character and have a bit of roleplay while rollplaying. I'm just looking for statistics wizard(s) to give me a good base to work with.
I'm sorry, I read your text 3-4 times but didn't understand well what you are planning to do or asking (I'm sorry) ...
<Snip>
I'm focusing more on storyline when gaming RPG (try to give a good time-show to players). Not focusing on the number of targets or the range of targets. If you want a suggestion, I would try not to use too much xenomorph at close range to your group (because they are very deadly). And PCs should avoid using too much action-rolls in the game (to avoid stress dice). I suggest you use xenomorph to raise tension (increase the pressure or build the terror).
Enjoy your first game.
Above should hopefully answer what I am looking for. And yeah, TOTALLY focusing on the story, the xenos are more than deadly enough, I don't want a mass combat/TPK.