Jayce bug
Here's how i did it.
Started a game
Picked Jayce
While in lane, get near a minion while in gun form
Walk further away from the minion
Quickly switch to hammer form and hit the minion
You'll see how it works in the video

Here's how i did it.
Started a game
Picked Jayce
While in lane, get near a minion while in gun form
Walk further away from the minion
Quickly switch to hammer form and hit the minion
You'll see how it works in the video

He has had this "bug" for quite some time. I like to think of it as a feature. Enjoy your new skills.