Review informations
Category Replica Accessories
Subcategory Internal parts
Model Mosfet Kit
Brand Billy Breach
Propulsion Electric
Cost 10 GBP
Size 5 centimeters
General Informations
Creation date July 02, 2012
Views 5746
Comments 0
Likes 1
Language English
Confidentiality Public




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I don't often do reviews, but I have a great deal of respect for people that go out and spend the time and effort to release their own thought out product. I have even more respect for those few that do this simply for the benefit of their community and it is this reason why I am writing this review.

Mosfets aren't a new thing in airsoft. They now come with a great deal of features, form factors and brands. There are good ones out there and there are a whole lot of bad ones.

Billy Breach is a UK Scotland-based airsoft mechanic who has released a very cheap, basic but surprisingly tough little mosfet for airsoft applications. While it does not include such features as 'Active (or passive) Breaking' or any of the 'smart' mosfet features which are becoming quite common, what we are left with is a small, tough and most importantly CHEAP mosfet which does what these devices were to do in the first place - improve electrical efficiency and lower wear.

Price at time of writing:
£8.50 for just the mosfet itself
£10 for the Kit containing:
- Mosfet,
- Deans T-Plugs OR XT-60 OR Deans Connectors,
- signal wire
- 3x spade connectors with insulation.

- 50mm x 17mm x 15mm
- fits easily in a stock tube - can almost fit 2 side by side

What is a mosfet?

A mosfet takes the electrical load away from the horribly inefficient trigger and tappet plate assembly, which can and does wear out with use and is one of the biggest sources of resistance in the modern airsoft rifle. Instead, it passes the power through itself, a ‘solid state’ switch and benefits from having a tiny resistance. This leads to higher battery usage efficiency and a higher rate of fire.

A mosfet can be considered as a ‘free’ upgrade - that is one with pretty much NO drawbacks and is ABSOLUTELY vital if you are thinking of using higher voltages such as your 11.1v Li-Pos and your 10.8v and 12v NiMh cells, as these sorts of power levels cause much faster degradation of the trigger contacts and cause excess heat in the switching area, which the mosfet prevents as a result of the electrical benefits mentioned above.

Airsoft mosfets come in many flavours, from regular to ‘Braking’ mosfets, which are designed to stall the motor after trigger release all the way up to ‘smart’ mosfets, which are coupled with a microprocessor in order to give you the more advanced and exotic features.

Now what about this Billy Breach mosfet?

Billy Breach’s mosfet is a no frills, single chip switching mosfet. In laymen's terms, it is designed to solely improve the efficiency and durability of the rifle’s electrical system. It forgoes unnecessary features such as Braking as this is both harmful for the motor and completely unnecessary, as there are better ways to deal with overspin.

Being a simple mosfet, it cuts down on size, cost and production time, which are all great features. And as far as installation goes, once I had purchased the unit II received a email with a great set of instructions in PDF format - very clear, well illustrated and required very little work.

What makes it different?

Billy managed to create a great mix of value and performance. At time of writing, he is selling his units for £8.50 (£10 for a kit with connectors and heat shrink), making this the cheapest mosfet on the market. For your money, you get a fet based around the IRF3205ZPBF chip, which has a great balance of cost and power. It can handle much higher current drain than the classic 1404Z, and whilst being somewhat weaker than the current staple of Fireworks, AWS/BTC and Extreme Fire, the 3034, it is about 33% cheaper and does the job admirably.

In addition, Billy has bucked the trend and included the TVS diode in his design. This little guy is able to filter out some of the scarier voltage spikes generated by the motor AND it goes some of the way to mitigating such issues as reverse wiring and some short circuits. The TVS seems to show up less and less in modern mosfets due to the fact that it is integrated within many of the mosfets. But these internal ones aren’t really up to the job, so a dedicated ‘protection’ TVS diode IS needed to prevent your mosfet from randomly going *pop* and scaring the bejesus out of you! To me, this part alone makes this unit worth consideration.

So What Can it Do?

As far as performance and capability goes, it passed my tests of a 7.4v and 11.1v (both 1200mAh, 25C) very nicely and I even threw the curve ball in of my P.O.S. chinese 7.4v 3-5C 1200c discharged down to about 3.5v/cell to see if it coped with low voltage (some older designs used to show signs of extreme heat at low voltages) and didn’t notice anything out of the ordinary, other than the gearbox barely cycling as usual, haha! So yeah, it shouldn’t explode, no matter how crappy your batteries may be! After having a chat with Billy, he said that he has bench-tested it with an 18.5v LiPo and while the unit got pretty toasty, it didn’t fail, which is comforting to know.

Finally, he offers his mosfet in 2 flavours - plain with bare wires, left for you to solder together and in ‘kit’ form, including a very nice Ribbed pair of XT branded Deans connectors, 3 sets of male and female Spade connectors to disconnect the mosfet from the gearbox and enough wire to connect it all together. This kit form is very useful for front-wired M4 variants, as the spade connectors he uses do fit through the Delta ring, meaning that disassembly of the upper and lower is made much less painful.

Any Negatives?

My only complaint was that the insulation that came with the spades was a little awkward to use. Trying to get it to overlap and cover both spades was nigh on impossible, so I used some heatshrink on the female spade and only used the provided removable silicone insulation on the male wires. It is worth mentioning that mine was an early design and he has since refined his build process to do the same.

Another point worth noting was to do with the arrangement of the wires. The kit is designed to be a 5-wire, so 2 to the battery, 2 to the motor and the signal wire branches off from the positive motor wire. This has the benefits of being REALLY easy to fit, by just re-soldering a single wire in the switch and this makes front wiring a damn sight easier because there are only 3 wires to try to squeeze through the hole. However, space allowing, I prefer a 6 wire design which has a 2nd (positive) signal wire branching from the connector closest to the battery instead of the trigger block, since there is less motor noise back there. But as you can imagine, this is easy to do yourself, but I include this point for the sake of completeness.

To do the 6-wire mod, run the two thick power lines straight to the motor. Run the thin data wire from the Mosfet to the switch as normal, but then run a second thin wire from the positive contact of the positive battery connector all the way back to the OTHER trigger contact. Easy as that! But it is more wires to deal with and you need to get your hands on another connector.

Build Quality and Workmanship

Not really masses to say here. The unit came well soldered with no visible cold welds or crappy crimp jobs on the connectors. Billy used high quality heat-shrink, covering the unit in 2 layers of thin heatshrink and one more protective thick layer on top, so there is little chance of something pinching through and creating a short. Also, the heat shrink is moulded in such a way as to keep the wires well apart, meaning that if you somehow manage to overheat the unit hot enough to melt the solder, the wires are slightly less likely to ping off, weld together and create a short.

The load bearing wires look to be 18awg silicone, but due to the very short length (3cm or so) it makes next to no difference in resistance and I felt no heat after prolonged bursts of Full auto and some semi-spamming with an 11.1v.


Buy it! It’s a mosfet for a tenner and under! It’s tough, it’s unlikely to randomly explode and even comes with all the parts and connectors you need to fit it. You are also buying it from the guy who builds it, so if you want it to be modified, explained, improved or to come with any extras in any way - he’s right there!

- Cheap!
- Didn’t fail on high or low voltages
- Kit comes with everything you need
- Includes a TVS protection diode
- No unnecessary active breaking
- Based on the 3205z not the 3034, which is a little less tough
- Spade insulation was fiddly, but this was sorted in newer models
Esthetism rating: 6/10
Performance rating: 9/10
Precision rating: 8/10
Accessories rating: 10/10
Quality rating: 9/10
Overall rating:

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