That looks great! It looks like a proper injection moulding screw with 3 different zones. What would you recommend this be made from? Stainless? And how critical is the clearance between the barrel and the screw? Obviously it needs to be tight to maintain pressure, but does there need to be a gap to avoid seizing, especially with the temperature gradient? Can the screw and barrel be made of the same material, or would you recommend a different material for the barrel, maybe bronze?