Originally Posted by MACdanstaface
I built other weapons (the first one I built was the grenade football) and still had the "handyman" achievement pop up no problem...
This. I had also built the Flamethrower before I built any of the new weapons.
Seems totally random at this point. It unlocked perfectly for me after I built my last "new" weapon, but my buddy can't get it to unlock at all.