Rogerborg

Thing is, many guns come with metal-racked Pistons out of the box now.  Specna Edge and the newer CYMA AKs spring to mind (I have both). How many guns will end up shitting themselves (completely) because the user is unaware of what's going on inside their gun? Who knows... but I suppose it keeps Airsoft techs gainfully employed.

My ICS guns came with plastic-racked pistons though, which is handy. 

Yup, my Ares guns came with steel rack pistons, my honey badger got the gearbox rebuilt and it runs smooth, the 009 (which I sold) completely destroyed the gear set when it stripped.

I get the point of having the last 2/3 teeth towards the piston head made of metal, after all they're the ones who have to bear the most pressure (when the spring gets cocked), but makes no sense to have the full rack being of metal..

some interesting points he makes, for example about hop overheating on auto. i do wonder how much of an effect compression heating has on that as well given hpa's tend to take a bit longer to "warm up" given they're running pre-pressurised gas.

polymer pistons are fine if it's good polymer (insert rant about the quality of airsoft plastics), and the whole sacrificial part is a valid concept, in general i tend to buy steel racks but i won't replace a polymer piston if it's in good condition.

reminds me of my rc days where polymer gears are pretty common, even on the 1/5 scale stuff, i had one that ran for years although ironically almost every other component of the drive system failed. that was good short-strand carbon reinforced though (handy side benefit the carbon acted as lubricant as it wears).

but he's spot on about maintaining, it's why i like to encourage people to get into their own teching, you can save a lot of money time and headache if you're able to keep on top of maintaining your own stuff.