I have a very nice 16" mpx Sig barrel/piston assembly for sale. This came off a mpx carbine and does not have many rounds through it. It was replaced on the mpx with a shorter barrel. Looking to sell it as it isn't being used. Will also consider trades for optics: Eotech/vortex uh1 gen2/Sig optics (something for my MPX not looking for LPVO or standard scopes, keep in mind this barrel new is $650+)