ModelSetPrimaryPart failed because no PrimaryPartPart has been set error?

Model:SetPrimaryCFrame() failed because no PrimaryPart has been set, or the PrimaryPart no longer exists. Please set Model.PrimaryPart before using this.

I Keep getting this error ^

I set the models primarypart and I got that error so I tried wrote the models parent in a script, still doesn't work why?

Gun.Parent=game.Workspace

RunS.RenderStepped:connect(function()
	Gun:SetPrimaryPartCFrame(Cam.CFrame*CFrame.new(0,-1,2))
end)

The Gun variable is calling out the model.

Models DO NOT automatically set their own primary part. you have to set it urself. You can do so the same way you set a Part's parent. Either by script or manually do so urself