Looping trough a list of objects in lua - oop

Question

I'm writing lua to script inside a videogame called Dual Universe, I'm trying to loop trough an array filled with objects and call their methods but it seems to turn my objects into numbers for some reason.
Here is the error message: attempt to index a number value (local 'projectile')
it's in the for loop of ProjectileGroup:move(), where I call projectile:move().
--Projectile class
Projectile = {x = 0, y = 0, z = 0, six = 0, siy = 0, siz = 0, spx = 0, spy = 0, spz = 0}
function Projectile:new (o,x,y,z,six,siy,siz,spx,spy,spz)
o = o or {}
setmetatable(o, self)
self.__index = self
self.x = x
self.y = y
self.z = z
self.six = six
self.siy = siy
self.siz = siz
self.spx = spx
self.spy = spy
self.spz = spz
return o
end
function Projectile:move ()
self.x = self.x + self.spx
self.y = self.y + self.spy
self.z = self.z + self.spz
end
function Projectile:log ()
system.print('x: '..tostring(self.x)..'|y: '..tostring(self.y)..'|z: '..tostring(self.z)..'|six :'..tostring(self.six)..'|siy :'..tostring(self.siy)..'|siz :'..tostring(self.siz)..'|spx :'..tostring(self.spx)..'|spy :'..tostring(self.spy)..'|spz :'..tostring(self.spz))
end
--ProjectileGroup
ProjectileGroup = {projectiles=0}
function ProjectileGroup:new (o,projectiles)
o = o or {}
setmetatable(o,self)
self.__index = self
self.projectiles = projectiles
return o
end
function ProjectileGroup:add_projectile(projectile)
table.insert(self.projectiles, projectile)
end
function ProjectileGroup:move()
for projectile in pairs(self.projectiles) do
projectile:move()
end
end
function ProjectileGroup:log()
for projectile in pairs(self.projectiles) do
projectile:log()
end
end
projectileA = Projectile:new(nil,0,0,0,10,10,10,0.1,0.3,0.4)
projectileB = Projectile:new(nil,0,0,0,10,10,10,0.4,0.2,-0.4)
projectileC = Projectile:new(nil,0,0,0,10,10,10,0.1,0.05,0.1)
projectileGroup = ProjectileGroup:new(nil,{projectileA,projectileB,projectileC})
projectileGroup:move()