The inability to rediscover firearms and projectile technology is deeply frustrating. We have attempted to recreate it through combustion, magica, and even crude magnetization.
Currently the best we can do is fire pure magica or magica "explosives". This requires LARGE amounts of magical energy.
The basic principles of firing an object down a tube should not be so hard to re-create... It's as if the very cosmos conspires against us!
Perhaps a small wrist mounted trebuchet is possible.
-council on the Further Development of the Magical Sciences