OK, here is my shot at this:
S600
11500109 in Metal QTY 2 [orifices], these usually come in delrin, but I hear they can also be obtained in metal and are much better for tuning
I haven’t tried them or looked up the numbers, the G260 has a metal orifice so that may be where the news are coming from, would like to know myself although I haven’t had any issue with the plastic ones.
11600031 QTY 1 [knob assembly for the Gen 2. It is for a Gen 1 S600, but I have the Gen 2 air barrel and poppet/balance chamber/spring/etc for this already, hoping to convert the Gen 1 to Gen 2] I just bought two of these through Simon to convert a few S555’s to s600, about $25
OR, I was going to see the price on a later S600 metal air barrel if it would fit a Gen1/2 case...and see the price for a metal air barrel. If it can fit and price is cheap, then OK...if no fit or price is expensive, then just the above knob assembly.
I wasn’t able to get a price on one either
MK20
Latest [MK25] composite piston and spring [blue coating for de-icing], I thought it came as a kit.
Maybe the MK25 seat retainer, spring, etc to convert my QTY 2 MK20s to MK25s, if the parts are cheap. This would be P/N 41300020.
Although, I cannot find an MK25 schematic that is newer than 2004...so the piston/spring part numbers, I cannot get, readily.