"This Aps hybrid gearbox is great! When i received it, I immediately disengaged the blowback and installed a matrix m100 spring to reduce the stress as much as possible (the purpose was to make this gearbox last as long as possible on an 11.1v lipo). It fit into my dboys m4 perfectly and is running fantastic on a jg blue motor with an angel custom tbb. I give this gearbox my highest recommendation for the price. Just make sure to disable the if you are going to be running a high voltage battery because it adds unnecessary stress to parts like the piston.
"Gearbox internal review:
Gearbox shell - 3.5/5
The gearbox shell itself honestly doesn't seem that strong; I also own the Matrix QD gearbox, and it is a LOT stronger. Also, in order to fit my SHS 13:1 gear set, I had to shave off some parts with a Dremel, so if you plan on replacing the gears, I hope you have a Dremel. Definitely not the shell for a DMR set up, but I think it'll stand up to anything lower than an M140 or lower perfectly fine.
Air seal nozzle - 5/5
The stock air seal nozzle is FANTASTIC!!! It's made of CNC aluminum, it's strong, it's lightweight, and provides a VERY nice air seal. Definitely the most impressive stock air nozzle I've ever seen.
Cylinder head - 4/5
Very good stock cylinder head. It's made out of polycarbonate, but the stem is made out of a nice aluminum. It provides a nice air seal with the stock cylinder; add some Teflon tape and you won't even need to buy another cylinder head. It comes with a nice, thick SorboPad pre-installed; nice touch, though it doesn't completely correct the AoE.
Cylinder - 4.5/5
Good cylinder. It's metal, some kind of shiny-ish silver. It's nice and smooth on the inside, so less friction between it and the piston head. It has a port meant for a standard M4 inner barrel (363mm), which doesn't really suit my 509mm inner barrel, so I switched it out. However, if it fits your inner barrel length, there is absolutely no reason to replace it.
Piston head - 4/5
It's a really nice polycarbonate piston with eight ports, but the o-ring SUCKS BUTT FLUPS. GET ANOTHER PISTON O-RING FROM HOME DEPOT FOR THE LOVE OF GLOB. Once you do, it provides a very, very good seal, no need to replace this piston head either.
Piston - 3.5/5
Standard stock piston. One steel tooth, rest of out made of polycarbonate, last tooth removed to help with AoE. It should serve you just fine, though replacing it to better suit your set up is a good idea.
Spring - works as a spring
It's a spring. It provides springy powers. I didn't chrono with it as I immediately changed the spring, sorry to disappoint. If I had to guess, it's either an M110 or M120.
Spring guide - 3.5/5
It has a metal base with smooth, metal ball bearings, which is nice, but the shaft is made of polymer. This is the same for the Matrix QD gearbox. I just don't see why they can't just make a metal one.....
Gears - 3.5/5
I'm not using these gears; as mentioned, I'm using SHS 13:1 gears. These gears seem to be an 18:1 ratio, but honestly, they don't seem too robust. But like I said, I'm won't be using them, so I can't test them. They come pre-installed with a sector chip.
Wiring - 5/5
It comes with low-res wiring, and the trigger contact is awesome! Definitely don't need to replace the wiring.
Mine came with a broken trigger. Don't know if that's APS's or UPS's fault, but it's worth mentioning.
As stated above, I had to do some Dremeling to fit my SHS 13:1 gears.
The blowback doesn't fit with my G&P upper receiver, though I wasn't expecting it to, so it's fine.