Yeah its gonna get stickied.

Gotta give the credit to Joel from Spudtech for all these.
Spudgun Do's and Do-Not's
Let it be noted that PVC pipe/fittings are not intended to be used for the purpose of constructing spudguns.
First, please...
...do have fun with your spudgun. That's what it is for. If you think it is a useful tool for a task, or serving as an effective offensive or defensive weapon, please forget you even know what a spudgun is.
...do treat is as a real gun/weapon, although it is not such. Even if you KNOW it is not loaded or charged, it isn't funny to point it at someone else. This might scare that person, leading them a reason to point it at you in the future, perhaps charged...
...do launch potatoes in a safe locale. This usually does NOT mean a residential housing tract. A good rule of thumb is if you THINK (do NOT test your theory) you can hit your neighbor's house with something out of your launcher, chances are they will hear it and call the cops.
...do learn about how to safely build and operate them using this site and the many others out there that deal with spudguns and related activities. Ask questions. Although I don't have all the time in the world to address every question I try to answer any I feel relevant. Make sure to check out my FAQ section.
...do always make sure you have enough spuds and fuel for an outing you have planned. Nobody wants to be labeled as: "...the guy who ran out of spuds and/or hairspray and there was still daylight left!" NOT cool!
Following...
...do not use a spudgun in a reckless manner (you can see this coming, kinda reciprocal of the above rules). Many instances exist when, even 'just once,' it was fired at something, or where someone else heard it and got scared, and the cops get called.
...do not use a spudgun in cold weather. This means less than 32ºF (0ºC) for PVC launchers. ABS launchers can go a bit colder, but not much colder than 0ºF. The plastic gets too brittle and it might shatter on you.
...do not use it in very hot weather either. Temps above 100ºF should be avoided as well, as the plastic's physical strength starts to precipitously decrease above this temperature.
...do not 'rapid fire.' High temperatures applies to multiple firings as well. Say a continuous duty of one round every minute, or 'rapid bursts' of no more than three rounds, with a five minute wait afterwards. This of course only applies to combustion launchers.
Not to be outdone by the previous rule, rapid firing of a pneumatic launcher can lead to cold-brittle failure, even on a hot day...WHY?!?! Dumping a tank of air rapidly causes a rapid decrease in the air temperature. This cold air cools the plastic, and depending on how big a tank/pressures reached and a lot of other factors, can really cool the pipe down. This does NOT make a good refrigerator for beer, just be careful, no faster than one round per minute.