Mad bull "utimate (FAIL) hop up unit!"
 

yah so, turns out they dont work in a classic army or a dboys metal body, gay, the worst kind of gay. i tried a bunch of different brand mags thinking that might be the problem, hell i even swiched out the nub, but still, the old plew-plew-blah sound. really disappointed, anyone else having troubles with these?

elaborate on the "dont work" part.

does it fit properly ?

well it fits in the recievers without issue, but i seems to pinch the lips of the hop up bucking, and, the "nub" that pushes down on the bucking, seems to be to big, because when the hop is "off" it still allows the rubber nub on the bucking to portrude, but after i swapped the nub out with a smaller one, it still misfed.

Mine worked fine in a DBoys M4 I used to loan out, sold the gun not long ago though.

I have no issues with it in a stock CA metal body. I noticed that the rubber was not flush when I installed it so I just used a pair of tweezers to straighten it out.

best to use the MB rubber and tight bore barrel for best fitment. I originally had the guarder clear in with a MB TBB, but found the tolerances too great causing the rubber to 'flap' a bit on every shot and it eventually tore the lips. swapped in the MB blue rubber and all is good. also using the SCS bucking instead of the standard one that comes with it.

yup that seems to be whats happening, the bbs are catching on the lips, i tried two different rubbers, one is king arms and the other is a systema, tried the stock classic army barrel and a mad bull black python but both jammed, ill use your advice and try the blue rubber, and swap out the bucking with the SCS, thanks man.

you can use any bucking. I just chose to use the SCS.

tight is an understatement

Two hopup rubbers...near identical but the thickness of the lips on one were a smidge thicker than another. 100% jams with the thicker one...perfect feeding with the other.

You can test "feed" before you reassemble by just placing a BB on the lips when it's all assembled and gently pushing it a touch with a stick/rod/etc...it should pass nicely. If it needs to be forced through...it'll probably jam.

yup

exactly what mines doing. a Stronger mag spring may help. Some one told me to oil the hell out of it?

You can remove the rubber but you will loose a few bb's every reload.. I'm still looking for a fix. I dont feel like ordering 10 different things to try.

Shawn

IMO don't use the o-ring on the bottom.
And I did notice it was tighter than a virgin trying to get the barrel in the hop chamber. And those madbull rubbers are crap lol
And I also noticed it doesn't like to sit all the way back in the hop chamber, it's hard to get the barrel grooves to the right spot for the C-clip.
Otherwise it works okay, but you definitely need a different hop rubber, and I used the stock CA clip to hold the barrel, it's thinner than the madbull clip that comes with it.

Yeah it seems that may be the best choice for now. It's to bad. Great idea