I'm not suggesting you should change careers and become a bank robber, but there are times when it's legal to break through the wall of a vault–as in this project to create egress in a bank that was converted to a library. The first video below shows the work being done. What grabbed me about it was the use of the Micro-Blaster, a system that relies on a pneumatic or mechanical head to detonate blank cartridges that have been placed in holes drilled in concrete, masonry, or stone. This is more or less what miners and blasting contractors do–only this is done on a much smaller scale and without the need for a blasting license (at least that's what the inventor says).
Here's how it works: The contractor drills a 5/16-inch hole into the material, cleans the hole, and then places one or two cartridges inside. The cartridges contain gunpowder and have built-in primers. The tip of the Micro-Blaster head is inserted after the cartridges and seated against them. Inside the tip is spring-loaded piston that functions as a firing pin, and can be activated by a blast of compressed air or the pull of a lanyard. When the piston hits the primer the cartridge goes off and blasts a small chunk of material out of the wall.
I can't vouch for the system because I haven't used it–but it is fun to watch. It's too small-scale for the vast majority of demolition and blasting tasks, but might be a viable solution for those rare instances when it's not possible to use wall-cutting saws or machine-mounted breakers. The demonstration (see second video below) of how to micro-blast ledge that is protruding into a roadway is cool because he is able to do the work without electricity or heavy equipment.
I emailed Carroll Basset and asked how he came to invent the Micro-Blaster. He said, "I needed a tool that could break rock on a relatively small scale to open caves for exploration and mapping as well as a tool to modify passage for cave rescue. I have worked construction when younger and been around blasters, my father had a Uranium prospecting phase which introduced me to dynamite at about age 12." Lucky kid–what 12-year old doesn't like to blow things up (especially with dynamite)?
In response to a question about regulation Bassett said, "We are exempted from the Federal Explosive Regulations so Federal Licenses are not required. Massachusetts requires Micro-Blaster users to hold a State License. Beyond that we are unaware of regulations governing our products."
You can find a list of vendors on Bassett's website. A single head kit lists for $660 and a three-head kit for $1799. Cartridges are sold in boxes of 100 and go for $2.10 a pop (pun intended).
Cutting Through the Wall of a Vault