This is Part One of Firing Pin Guns. This is, by far, the most popular mechanism of K'nexers. I feel like this and part two are going to be some of the most important parts to this guide, so read carefully. I hope you find what you need here and good luck!
1. Single Shots: A single shot, in K'nex, is the most basic pin gun. The single shot pictured here is KILLERK's original K'nex pistol
: a staple throughout the K'nex gun community.
How it works: A firing pin is pulled forward by rubber bands. It requires you, the user, to pull it back until is stuck behind a trigger, which is usually pulled by more rubber bands in some fashion. You then load a bullet into the barrel; if your single shot is exceptionally well built, it will have a bullet lock, which keeps the bullet in the barrel.
Once the trigger is pulled, the firing pin is unstuck, and the firing pin flies forward and rams into the bullet. The bullet, because physics tells it to, will fly out of the barrel and hit something, hopefully, at what you were aiming for.
2. Magazines: A K'nex gun with a magazine of some kind is one of the most built K'nex guns on Instructables. Shown here (the second picture; the numbers match up with the order of pictures) is KILLERK's basic magazined pistol
(It is the last gun in the slideshow). As we will learn later, that magazine is a clip-on, removable magazine.
How it works: Remember the single shot concept? You should read through that again. Did you? Ok, good. Now, a magazine is being added. So now, when you pull the pin back, it will slide past a bullet in a magazine, and the bullet will be pushed into the chamber by rubber bands. Now, continue to pull it back past the trigger, and now you've got yourself a shot to fire. Just keep pulling the pin back, and bullets will keep being pushed into the magazine, giving you a much faster reload time than a single shot.