Systema Metal Hop Up Unit for the M-16 / M-4 Series. All metal body, plastic gears, etc.
I have to say that this thing is pretty much a piece of junk. I don't think that it was because I got a bad one. It works as designed and intended. After I realized it was slipping, I broke it back down, gave it an inspection, reassembled, and even tightened the screw a little more and then reinstalled. The slipping improved, but was still apparently there. I disassembled it yet again to look at the mechanics of the gears, and noticed that it was a design flaw internally. The curved "comma" shape to the riser to the fulcrum makes for easy slippage. This also tipped me off to something I had suspected it was doing when adjusting, and that was it also makes a 360° revolution and pops back down to the lowest setting, which means that if you are are trying to go to the highest hop and back it down for adjustment purposes, it would slip while turning it, or slip (even back) when the rifle was shot. to make things a little frustrating.
I took my stock (plastic) G&G GR15 Hop-Up, played with it, inspected it, took it apart, and reassembled it, and installed it, and shot it. It worked marvelously; as a hop-up should be working. I am disappointed that my stock plastic hop up performs better than my systema metal hop up unit.
The other hop ups that I have toyed with do not have a 360° rotation, and will stop when adjusted all the way up and all the way down, and as far as I can tell don't have major slippage issues. Being as though this is pretty unique; I am rating this product as bad, and for $40 - generally a bad investment.
All Metal Body
Appears to make an excellent seal.
Mags don't have a problem with it.
Full 360° rotation of the sprocket with riser for the fulcrum.
Rating: [1 of 5 Stars!]