One of my first jobs was to sandblast newly assembled car carrier trailers (eventually became anchor clankers).
this was a large setup with full hood and cape with supplied air and a 'deadman switch' on the nozzle which looked a bit like a fire hose.
One of the employees brought a door in a car door and wanted to get it sandblasted. I told him that I had never blasted sheet metal but he insisted that I try.
I turned on the air and almost immediately blew a rather large hole in the door on the first sweep.
The abrasive used was 'black beauty' and it can be aggressive with high pressure air.
On the other hand I have recently blasted sheet metal from my 8N with a small gravity feed blaster with black beauty with no problems.
hope this helps,