if you want to update your jg rifle from an older gearbox style, then this is probably the best way to go. i was personally curious about how far jg had come in the past few years, so i decided to buy a full gearbox instead of a $250 rifle. from what i saw in this gearbox, jg has many of the ideas down that are necissary to make a quality gearbox. they just need to work on their quality! you absolutely do get what you pay for. this is only $90 while systema is ~$300 for a reason.
first off, i installed this in my CA m16, the older version. if you are getting this for a CA, replace the selector plate. i had some trouble installed the gearbox because of that. the selector switch and selector plate do not mesh perfectly. the wiring system is excellent. however, the mosfet is literally the bare minimum for what you would call an airsoft mosfet. it consists of a simple mosfet switch (to protect the trigger contacts), a transister (to store energy and decrease response time), and a resetable fuse. the houseing of it is made of plastic and the circuit board is very visible and accassable.
the description says this gearbox is for an m16. that is more or less true. it comes with a type 2 cylinder, ported for an m4. so a type 0 cylinder is recommended with the gearbox. the cylinder assembly is decent, minus the piston head. the piston head did has bearing installed, which is good, but the head itself is a joke. do yourself a favor and replace it with a modify head or other brand.
the gearset is decent, with a sector chip installed. the tapet plate is a bit different; the lower half of the wedge that catchs on the sector chip has been removed. no idea why. the gearset hardly had room to be shimmed, less than 0.1mm on either side of each gear. i was forced to leave shims off of the bevel gear which resulted in a painful time tuning the motor. this gearbox does not come with a motor, so i recommend buying a jg motor for this. i had a hell of a time finding a motor pinion gear that is completely compatible with this thing.
the spring is supposed to be an m130, but i feel it is closer to an m100. it is plenty stiff, but it is shorter than most stock springs. when i first installed this, i was getting only 250-300fps. as joke in gearbox standards these days. with some tuning and the installation of an air seal nozzle and a new piston head, i got it up to about 350fps consistantly. by then, i had spend nealry three hours working on this box. the next day (today) i will install a new gear set and try my CA motor on it, as well as replace the spring. with an luck ill have this shooting ~400fps in no time.
if you are looking for something to update your old jg gun, this is a fine gearbox for that. but stay clear of it if you are looking to upgrade a higher end gun. this thing will end up draining your pockets like there is no tomorrow. src or bravo gearboxes cost a bit more, but they are better quality and worth the extra money. but if you like modifying parts or having a project gearbox, you might want to look into this.
-decent construction, lots of good ideas from jg, just not executed with quality
-nice wiring/switch assembly, can tell a slight increase in rof and decrease in response time because of the cheap mosfet
-strong, but painful to shim, gearset
-large tamyia connector, not deans
-selector plate incompatible with CA m16
-poor stock air seal
-pain to shim, no more than 0.1mm on either side of each gear, if that much
-m130 spring is short and seems less powerful than it claims
-metal spring guide, not bearing
-cheap feeling piston (element piston with same design it higher quality for $14)
-cheap bearing piston head, lower quality than previous jg version
-gearbox requires significant tuning to get it up to playing standards, as well as many replacement parts
you get what you pay for. spend the extra money and get a nicer gearbox.