Step 1: Here Are the Parts

The Launcher is constructed out of a PVC pipe, 1 x 2 x 2" block magnet, Ø60mm
neodymium pot magnet and couple of nuts. The projectile is a small dart. 1/2 inch sphere neodymium magnet acts as a striker that catapults the projectile

Step 2: Assembly

Once you got the right ingredients, assembling the launcher is a really simple task. Attach 4 nuts, or other convenient sized metal parts to one of the big magnets. Then mount the pvc pipe in between the nuts. (Instead of metal nuts, smaller magnets could be used to join the two bigger magnets and pvc pipe together. Note that there doesn't necessarily have to be two big magnets, one is enough! Attaching two big magnets is kind of dangerous business so I attached a bolt to the ring magnet and held the bolt in my hand when combining the two large magnets and the nuts and pvc pipe this way I had some distance between my fingers and the two powerful magnets

The dart goes to the front end of the pvc pipe. The flight stabilizer of the dart need to be the right size so it fits nicely, in to the pvc pipe, not too tight not too loose.

When firing I just release the 1/2" sphere magnet into the pvc pipe.

Air rifle target or an other target makes shooting more interesting.

Step 3: Mechanics

The operational priciple is really simple. two big magnets have the same magnetization orientation and when the sphere magnet is released it jolts into the pvc pipe with force and catapults the dart through the other end.

If I have had a diametrically magnetized cylinder magnet. I would have used that but sphere magnet was the next best thing.

I decided to keep the design very simple, but I have to say reloading this is pain in the ass. A pulling device attached to the moving magnet would make this more clever and easy to reload.