I enjoyed the James Bond Special and was specifically interested in the shooting a propane tank with a 9mm. Which in itself, sounds feasible, but of course no explosion, since ammunition does not spark and if it did, its not at a temperature or the frequency at which the gas will ignite. What the experiment needed was armor piercing 9mm rounds. 9mm rounds are subsonic and do not work on the same principle as high powered ammunition. If you look at the Jane's Gun Books, you will see a Russian sniper rifle based on the 9mm, which says it will defeat ALL levels of body armor, including steel plates.
To make the James Bond propane tank movie myth work, you would need use armor piercing rounds to rupture the tank and throwing a road flare in the vicinity of the tank and see if an explosion would occur. Granted, I loved the fact that the Mythbusters used a Gatling Gun to do the job to blow it up. I love explosions, lol.
In the movie re-make Dawn of the Dead, the antagonists used small propane tanks and strapped a road flares to it, after shooting the tank, it automatically exploded, making them have a get away from their flesh-eating enemies. If the Mythbusters revisit this, thats the way to go about it.

In conclusion, use armor piercing rounds next time in the 9mm. I think James Bond would of used specific ammunition. Putting in more gunpowder and an armor piercing projectile.

awesome idea... run with it.

I would agree with the armor piercing rounds. My suggestion for the 9mm hand gun wold be 9mm BNT HP7 made by Nammo. International Cartridge Corporation has a super duty 9mm round called Gren elite that will pierce level IIA Ballistic body armor. Of course the round would have to be API to ignite the gas.