First major upgrades - KA Sig 556

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LazzurusMan

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So after having a slight trigger issue with my KA sig 556 I decided to take the plunge and fix it myself. After opening the gearbox i realised i needed to clean EVERYTHING (ex display model, probably the first time itd been opened), and re l8be the very dry piston. After a few mistakes and reopening the gearbox about 5 times i feel pretty confident doing so, so im planning on making a few upgrades, mostly to increase trigger response and maybe rof. 

Im looking for suggestions on motor, mosfet, shim tutorials, aoe tutorials and maybe a decent but inexpencive piston.

Many thanks in advance, hopefully i can do this all before i next skirmish :)

 
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SHS Hi torque or ASG 30k if you have the money. SHS 13:1 gears. SHS blue 15 tooth piston with half metal rack or Lonex red. Cylinder ported to suit the barrel length and BB weight. O ring air nozzle and preferably a cylinder head from the same manufacturer if it's available. Careful AOE and shimming adjustment. Fire storm basic Mosfet which comes with 16awg wiring already fitted and a thermal fuse. It's also tiny enough to fit almost anywhere. Decent 7.4v lipo with the ability to deliver at least 35 amps .

This will get you snappy trigger response ,a very decent rate of fire without any risk of the internals smashing themselves to pieces and it should last, as long as it's carefully put together .

 
Ive read that you can get a decent trigger response and rof without changing the gears, is it really necessary? Also how do i got about porting the cylinder?

*edit* Also im planning on running an 11.1, if that wouldnt be too over the top for the box.

 
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I dont quite get what it is you showed me, but thats the sort of thing im going for in my sig.

 
If you don't want to change the gears then there are high speed and torque motors available that'll give a response boost and a rate of fire increase, but that's not a build I've yet attempted.

If you're going to use 0.2g BBs then you just buy the right cylinder for the length of barrel you're using, but if you're going to the trouble of rebuilding the gearbox then 10 minutes spent putting a hole in the right place in the cylinder to give the correct air volume for the length of barrel and the weight of BB is one of the little differences between good and properly sorted. I build for 0.3g ammo so I aim for a cylinder volume of 2.27 times the barrel volume. Once the AOE is done work out the compression length in the cylinder and cut a relief in the side so the cylinder can't start compressing air until the right spot.

 
What's in the vid is the build I described on my M4, just so you can see the type of trigger response and ROF that combination gives.

 
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I think ill just get a new cylinder. Im having to order new gears, mosfet motor etc, so spending a little more for piece of mind isnt a bad idea.

 
I buy a full cylinder and put the port in at the right place. Not difficult with either a drill or a Dremel. But this only applies if your barrel is shorter than around 340mm. Above that you want a full cylinder regardless.

 
I think mines quite a bit longer. Ive got the extended sig 556. So i need a new set of gears, a good shim job, a shs motor, mosfet (any ideas what type, brand etc?), a new piston and a slight aoe adjustment. That should give similar results to those you showed me in the video?

 
The build in the vid is: ASG CNC 30k motor (but you can find the SHS Hi Torque for half the price and it'll work pretty much the same, maybe not as smooth), SHS 13:1 gears, SHS blue 15 tooth half metal rack piston and aluminium piston head (because I had one laying around, the plastic ones are pretty good and lighter) , modify M100 spring (just use your stock one, if should be fine), SHS cylinder head and o ring air nozzle, SHS tappet plate (again, your stock one should be fine). Other bits are the Fire Storm Mosfet (£10, pre fitted with decent wire... bargain), Deans connectors for the battery, and high current 4mm bullet connectors for the motor.

View attachment 22147

I had the room to do this inside the grip and it means I get rid of the tiny motor connectors as the leads are now soldered to the motor terminals but can still be disconnected.

The Mosfet lives in a recess on the back of the gearbox.

View attachment 22148

You don't have to go to this much trouble, but it makes everything easier in the long run.

The final ingredient is 7.4v lipo batteries. The rest is careful assembly and watching a lot of YouTube guides, being methodical and asking the right questions. The first time I shimmed a gearbox if took me two hours, a few down the line and it takes about half an hour.

 
Thank you very much. Hopefully ill start ordering the parts on thursday :)

 
So the mosfet you suggested isnt gonna fit in my gun, unfortunately im a little short on space. Are there any mosfets thatll replace the trigger system in a v3 gearbox?

 
LazzurusMan said:
So the mosfet you suggested isnt gonna fit in my gun, unfortunately im a little short on space. Are there any mosfets thatll replace the trigger system in a v3 gearbox?




 
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Short answer - no.

But the mosfet doesn't have to go inside the gearbox. Extend the trigger contact wires and put the fet in a space where it will fit.

 
Have Dremel can make things fit! But as above there will be somewhere out of the way it can be secreted.

 
Actually theyve got the gate nano abb in stock for £25. Ill pick that up instead. Even gives me the deams connectors i need to change the gun over.

 
If you're going with the Hi torque type set up you wont need the active braking of the AB, the SSR will do fine. I installed one in my son's gun and it fits fine in the buffer tube with stick batteries in the tubes of his Crane stock. There's no thermal protection built into the smaller Gate Mosfets so your tech should recommend an in line fuse to protect everything.

 
Just checked... The Gate doesn't quite fit in the buffer tube together with a 7.4v 1450mah stick lipo. The Fire Storm however falls in there and has the built in thermal protection . Ask your tech for his advice.

 
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