You can't shoot a propane tank and make it explode, unless you have some kind of incendiary round. Most of the time when shot, a propane tank will just throw a plume of propane gas 40 ft in one direction. A normal bullet won't get hot enough to cause a spark. Propane tanks need an ignition source. This could possibly be achieved with a tracer bullet, which is accompanied by sparks that make the trajectory visible. Even then you wouldn't be guaranteed an explosion. On mythbusters, they theorized that the shooter would need to be far enough away for the bullet to build up enough frictional heat.  

https://www.youtube.com/watch?v=W4Ludqi81AE

In this video, they set up a burning candle next to the tanks, but it still took 10 or so shots before the leaking propane ignited. The explosion is pretty small and burns out fast. It seems that being about 300m away is  pretty safe as long as you don't get tagged by a flying shutoff valve.

What about a gas tank on a vehicle?  Nope!
Although a partially full tank would be more likely to explode (due to the presence of air) than a full one, the chances of this actually happening seem pretty slim. Apparently, even a pipe bomb in a gas tank won't ignite the gas (according to a guy claiming to be a firefighter on the internet!) It would need to embellished with steel wool or some other medium that could absorb the initial heat of the explosion and  carry that heat far enough away to where the air-to-gas ratio becomes favorable for ignition of the gas.

![](https://cdn.steemitimages.com/DQmf5j4gsVoBhvjSd8m97sq8TLJdLKrQhBjpGj8iY1P31UG/image.png)

There is another experiment where a cutting torch is placed over an oxy-acetylene tank and allowed to burn. Though the tank eventually ruptures dramatically, the force of the escaping gas is high enough that the flame is put out immediately.

That only works for because the tank is under high pressure... You can definitely ignite a vehicle gas tank with a cutting torch, as this fellow found out around 2:45.

https://www.youtube.com/watch?v=ykJ7ka_buH0

Though a fire extinguisher would have been better,  the fire was small enough that the hose was able to douse it. If the fire had been much much bigger, he would have needed a great deal more water than what a garden hose could provide.