metal shells

They're usually hand loads in cut down .50 BMG shells.

but ive ceen them in 12 ga though, last i knew 50 bmg shells arent that big

It's a common field expedient to cut down .50 BMG to use for 12 ga. If you cut a .50 BMG to 3" in length, they're the same OD and if done right, the .50 BMG shells run through a 12 ga smoother than plastic will. The powder charge for 12 ga is much smaller than it is for .50 BMG, so the shells don't deform and can be reloaded almost indefinitely.

so would a normal shotgun reloader be able do the job or would u need a speacial setup

It's all done by hand, but for safety reasons, I won't explain it here. I'm sure that if you were to utilize the internet and some reloading tables, you could figure it out on your own though.

Your gun's owner's manual specifies to only use ammo that is loaded to SAAMI specifications though, so be sure to follow those recommendations.