You'll be using the machine guns to shoot the safe which is wrapped up in a ball to make it roll along the spiral track. You can only do short bursts with a gun so that you don't end up with stray rounds hitting a crystal.
Start the safe rolling by hitting it with a machine as it rounds the corner on the left side. This is one of the tightest spots in terms of not being able to shoot early or late or you will hit a crystal. But at least they made the first part the hardest so that you can restart when you hit a crystal without losing much ground.
Once you get it to the first corner, you may need to hit it a couple times from a gun on the upper left (shooting towards the bottom right pig) to get it around the corner and onto the next ramp. Getting it "down" the 2nd leg is pretty easy, just don't start shooting too early.
The 3rd leg was the most annoying for me. You can only hit it with a short burst or you'll hit the crystals beyond. On this ramp it will roll back to the beginning if it doesn't quite make it over the 1st joint, where it can stop until you hit it with another gun, or over the 2nd joint to get fully onto the 4th leg. If it starts rolling back, just take a breath and wait for it to stop and try again.
The 4th and 5th legs are easy with not much danger of hitting a crystal. The only thing to be careful is not to give it too much speed since it can jump the railing and fall into the pit.
Now give it a solid blast to send it towards the dynamite and as soon as it is in range hit the detonator. If the safe doesn't get a good pace on it heading towards the dynamite, it won't get in range before a machine gun comes along and pushes it into the pit. Again, there are no crystals behind it so blast away to give it a good solid hit. You can also click on/tap the explosion icon in the top right to see the radius of the dynamite so you'll know when the safe is in it - but don't get your hopes up, the radius is small.