I have only shot this once, because I was too excited about making this- my first Instructable. It might singe the end of your gun slightly, but it won't blast your gun to pieces if you use the caps with moderation. So, just to say, I really can't be held responsible for any injury or damage etc.
Here are a few of safety precautions, and why I think they matter:
1. Don't point it in front of people- the 'firing pin' (actually a 6mm BB pellet) could bypass the caps and shoot straight out like if you were shooting at them with a BB pistol anyway
2. Don't put it next to your ear- it WILL make you go deaf if gun is cocked and it accidentally fires
3. Make sure gunpowder (or whatever they put in caps these days) won't spray out (potentially into peoples eyes/food)
4. I fired it in a bathroom- and the sound echoes like hell in a bathroom (ouch!)
So, I suppose I need to show you some basic ingredients to the Super Loud Cap Gun- these can be seen in the images for the intro by the way:
1. A BB Pistol and BB/Airsoft pellets
2. Some paper roll caps
3. Tape and scissors (or just a tape dispenser)
You can use a cheap BB pistol- in fact I would expect that you would much rather break a BB pistol that you got for £5 than a £100 gas blow-back. Oh- and I almost forgot- this Instructable is 110% non-obtrusive so you shouldn't need to open your BB gun up at all. It will still be a BB gun- it hasn't been modified.
Finally, if you make an upgrade to this design- please, please, please: make an Instructable out of it (and don't forget to put my name somewhere on it for credit) and notify me so I can make my own better.
Thanks, let's get started then!