Rotating barrel selection and in .22lr.
From Mail & Guardian SA.
A .22lr pen gun made from a $3 automatic center punch tool. The key ring is simply pulled back and released to fire. These same guns are being reportedly sold for $100 each on the streets of Sydney.
“3D printed firearms are no longer one shot wonder toys… They are serious weapons that can compete with their manufactured counterparts. Enjoy this in depth discussion with the anonymous heads of the decentralized design group Deterrence Dispensed.”
Full version at LBRY.