HHQ QC [OOC]
Let me describe this visually again and see if that helps.
There is a mountain side that holds beneath its rocky south-facing slope a buried Imperial ship. It is facing nose-down. It is between 1.2 and 1.5 kilometers in length when fully operational, but you don't know how much survived, or even what specific type of craft it is.
The terrain is completely covered in stunted fir-type trees - scores, even hundreds of years old, but none growing bigger than 1/3 the normal size of these trees. The tyranids are *mostly* located to the west/right of the buried ship when you arrive.
You approach from the east/left. You are 'halfway' up the side of the mountain, so as you approach the spur of the mountain that contains the ship, you are near what should be the tail section of the ship. Zilch has seen the schematics and pinpointed the location of where to breach, but as it is covered with scree, dirt, and stone, it will require some searching for the perfect spot to plant the charges.
Tyranids are aware of your presence and are climbing up the slope on your left, from the open plains where the Salamander and Tauros just did their distraction run. They are also swarming over the buried ship and so coming from your front [the west]. Those are much closer than the ones coming up from the plains. The ones down-slope from your position are mostly wounded survivors from the strafing run; the ones climbing over the spur are fewer in number but unwounded.
The tyranids can be any range from you that you want when you start shooting. They don't notice you, though, until you get to within about 200m of the target location. You cannot be closer than 60m when you roll for initiative; you have free shots before then, but if you start shooting early it may bring reinforcements faster.