Hey I've been working on puzzle 4 where you use the girder to get accross the gap then the shotgun to shoot down the barrier. Then you pick up the health crate and fall down. After that you use the jetpack to get the crate with the bunker buster and the parachute. The exit is down below and I've tried to use the bunker buster to bore a hole down to the exit but it doesn't ever make it far enough because it explodes before it reaches the exit. Maybe I am thinking about it completely wrong, but I am stuck and could use some help please.

The bunker buster can tunnel far enough. Use it on the left side. Look at the bottom of the tunnel and you will see the left side is flatter than the right.

Thank you for your help that worked on the first try.