Madbull Shark Hop Up Bucking


I recently started having problems with the hop up in my Classic Army M15A4 RIS, and figured that the hop up bucking (a Guarder Clear Silicone bucking) was worn out. I figured now would be a great time to do some empirical testing of the Madbull Airsoft Shark Hop Up Bucking.

Madbull originally designed this to fit their 470 gas powered rifles to prevent double feeding issues, but along the way they found that this hop up bucking would actually increase the velocity of the bb. Being that my M15 was now shooting a measly 300 fps (come on it’s a Classic Army, I expect more), this sounded like a quick fix that might work.

The Shark comes with two buckings, a clear silicone one and a black rubber one. The silicone one provides a better seal at the cost of easier wear and tear and shorter life span. The black bucking is much more durable, works with higher fps systems, but does not create as much hop in lower fps guns.

I opted to try the black hop up bucking with the “x” type nub. This “x” type nub (also called a “Fishbone spacer”), works similarly to the hop up nub in a Marui M14. By applying pressure to the edges of the bb as opposed to the center, you can apply more spin by being in contact with more surface area. Now one thing to consider, is that Madbull does state that the Fishbone spacer might not work in all AEG’s so you’ll just have to try and see what you get.


The bucking I am testing is made of rubber and is black. The included Fishbone spacer appears to be made of rubber as well.


MadBull Shark hopup bucking1This hop up system has two main features. The first is the Fishbone spacer we talked about before. This is what applies pressure to the hop up rubber and in turn applies pressure and spin to the bb. The other feature is the three fins located on the hop up rubber, where it interfaces with the gearbox air nozzle. These fins are what prevent double feedings.

The hop up rubber also has the usual groove that allows you to position it in place correctly on the barrel and inside the hop up unit.


MadBull Shark hopup bucking2Okay, I’ve seen other people talk about this hop up bucking before, but with nothing to support their claims. I’m here today to put some numbers and facts to my own claims and empirically prove the quality of this piece of equipment.

I had the guys at Airsoft Atlanta install this for me. Frankly, I hate dealing with the delta ring on my AEG, so I’d just rather have them do it for me. They kindly installed it for free! Thanks guys. During the installation we came across the first problem. The Fishbone spacer was too wide to fit in my stock Classic Army hop up unit… or so it seemed. After a bit of fidgeting they were able to fit it. After testing, they chronographed it at 330 feet per second. Now that’s a 30 fps gain. Now keep in mind, my previous hop up was well used. I know this isn’t exact, but I’m estimating that the difference in velocity between the hop up buckings (when the Guarder was new) to be about 20 fps or so. That is still a big gain for a $10 part.

Now let’s look at the range. I took it out in my back yard where I have about 130 feet of clear space to shoot that is ever so slightly up hill. With my previous hop up bucking installed I was getting about 100 feet out of my gun (nothing to write home about). So what did I get with this one? Problem number 2. The first shot looked good, but I played with the hop up setting anyway. A little more… a little less, and realized that it wasn’t doing ANYTHING to change the amount of hop! The range appeared about the same as the previous hop up bucking (but noticeably faster).

So I sucked it up and dismantled the hop up unit and took a look. Everything looked great, but as I was putting it back together I noticed that because of the extremely tight fit, the Fishbone spacer was not moving, just flexing, when I adjusted the hop up. At this point I just wanted it all to work right so I broke out the sandpaper. After using some 800 grit sand paper for about 10 minutes (evenly sanding each side of the Fishbone spacer), I found that 800 grit was too high. So I found an emery board and started using that to sand down the sides. That worked quickly and soon I had a Fishbone spacer that fit. I putt the assembly back together and looked through the barrel from the gearbox end, and turned the hop up to see how well it worked. It seemed to move back and forth as it should, but not enough. So I took a tiny piece of silicone insulation from some silicone insulated wiring (used for R/C cars), and cut a bit off. Now I cut that circle of insulation in two, creating two semi circles. One of these I cut down till it fit neatly inside the top half of the Fishbone and only ran across the top half of it. This would allow my hop up unit to put pressure more evenly across the Fishbone spacer. Did it work?

Trial number two. Now I’m hitting about 120 feet with it consistently. The hop up is more responsive to changes I make, but set properly I still have a nice flat trajectory. I did notice that shooting short bursts on full auto allowed for greater range than semi auto shots. If anyone knows why this might be, please comment.


The Madbull Shark Hop Up Bucking might just be all they say it is. While it wasn’t designed with anything but the 470 gearbox in mind, it seems to have its place in some AEGs. I did find that you might need to do some customizing to the all the components to work together properly, so you must be ready to either have a tech do some extra work, or be willing to fiddle with it yourself. Once installed and properly function it works well and I recommend it. Hopefully you’ll see a gain in your FPS too!

tags: madbull shark airsoft review


2 responses

4 12 2009

“I did notice that shooting short bursts on full auto allowed for greater range than semi auto shots. If anyone knows why this might be, please comment.”

I know this is an older entry, but I figured I’d pipe up anyway. I think you were getting a double feed. Since you’re trying to use the same amount of airflow and pressure to shoot double the weight of normal, your fps drops by about a hundred +/-, resulting in a reduction in range.

I was looking at getting a set of these to help correct the same problem, though it seems that’s not gonna work. Still, the fps boost and trajectory leveling will be nice. Looks like I gotta buy a sector chip, oh well.

6 12 2011

Hayseed, not even close. Re-read what he said. Full auto was increasing range not decreasing it. No double feeding at all, that was the original reason Madbull designed the Shark Hop-Up system in the first place.

Maybe full auto creates an extra build up of air and thus more pressure?

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