Let's face it, explosions are fun. From firecrackers to fireworks to firearms to demolition, releasing a lot of energy in a short period of time is very exciting. The sound of the explosion, the flash, the blast, the smoke and flying debris are awe-inspiring and adrenaline-inducing. Lighting a fuse, pulling a trigger or pressing the red button gives one direct control over all that power.
An explosion initiated by launching a projectile at an explosive target ads extra dimensions the fun of the "bang". It makes it more challenging (you have to actually hit the target), but also safer at the same time (no fiddling with wires, switches, ropes, blast caps, fuses, primers, etc.).
Explosives are no joke, but although some are quite safe and can be acquired and used legally (look up "Tannerite"), they are not affordable enough for my taste. Fortunately, there is an even safer and much cheaper way to generate a very loud explosion without using anything even remotely related to explosive or firearms. Enter the humble and ubiquitous plastic bottle.
Plastic bottles that held carbonated drinks are the best because they are designed to withstand high pressure. The size and shape of the bottle doesn't matter, but bigger ones make bigger explosions. The procedure to turn an ordinary bottle into an explosive one is very simple and easy. Just drill or punch a 1/2" hole in the bottle cap, install a tire valve in it and pump it up to about 100psi (my pressure gauges all end at that pressure, so I just pump a bit above it).
Once pumped up, the bottle is as hard as a rock and explodes very loudly when hit. The loudness of the explosion is comparable to a shot from a high powered rifle or a shotgun. You don't even have to use a firearm to trigger the explosion - a BB gun, arrow, slingshot or even a blow gun will do.
The explosion, although very loud indeed, is non-destructive and practically harmless. I've had a bottle explode right in front of me when I over-pressurized it and it didn't do anything but create a loud bang. I wear glasses when working with them though. The plastic pieces of the exploded bottle are not heavy, don't fly far at all and won't break the skin even at short distance, but I don't want any in my eyes. My experience is that these targets are perfectly safe if further than few feet away.
- Tie the caps/valve stems to something. They are almost infinitely reusable.
- Type, material and length of the valve stem are not important. I've used short and long rubber valve stems, straight and angled screw-on metal ones, and anything in between. Any valve stem for any type of tubeless tire will do fine, providing you drill the appropriate size hole in the bottle cap.
- There are commercial versions of these bottle caps out there. They are no better quality than DIY ones, don't last any longer and are much more expensive.
- Some people create more/less elaborate stands for these targets to avoid loosing the caps and make them stay upright. I found that hanging them or tying them to something is much simpler, cheaper and easier.
- No glue is necessary, period. If the cap is not holding pressure, use a different (thicker) cap or drill a smaller hole. 1/2" hole works very well for me - it takes a little effort to pull the valve stem through it, but it's a tight fit and doesn't leak.
These are the same bottles, the left one is just pumped to 100psi :)