If you are looking for the best stock gearboxes, Krytac and VFC's 2015 H&K lineup are what you should be looking at. G&P's internals aren't that great. Tolerances are extremely poor. Krytac is a solid choice. They have good (for a stock gun) wiring and motor, and well above average internals. It also comes with a MOSFET so you don't have to worry about your trigger contacts burning out. Air seal components are mediocre. VFC 2015 H&K guns are also well above average in stock form. Their wiring is average, but they also have a MOSFET installed. Their motor is average, but their new gearbox internals are very good. I have yet to see any of the new components fail. Air seal is also as good as it will get.
VFC and Krytac both do the job well. I personally prefer VFC, but pick the one you think looks better.
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