M4 Build Questions

[jaykim99 1]

Hey guys, so I have an ICS Par Mk3 CQB (10.5 inch outer barrel) that I am trying to upgrade for trigger response and increase ROF.

Parts I have purchased so far:

- SHS 13:1 Gears

- SHS Sector Gear chip

- SHS High Torque Motor

- JBU M100 Spring/ Stock ICS M120 Spring

- Madbull Ball Bearing Spring Guide

- Turnigy 11.1V 1,800 Mah 25-40C LiPo

- Nukefet from BrillArmory

- Deans Connectors

 

Everything else is stock.

Some info about the stock parts:

- 6 (or 8?) metal tooth ICS Piston

- Type 1 ICS Cylinder

- Plastic Cylinder Head

 

So my question is, would this setup with the M100 spring cause premature engagement? What about an M110? My goal is to reach anywhere around 28-35 rps, with a max of ~375 Fps. I have heard that putting the M120 and short stroking would get rid of any PE, but I'm trying not to modify the gears at all. I was also told that short stroking may cause some issues regarding cylinder volume, as well as tappet plate engagement issues. Anyone have any ideas on what I should do? I'm mostly going to shoot on semi, as my local fields don't allow for full auto, so the PE shouldn't be too big of an issue, but I still want to be able to shoot full auto without destroying my piston. Thanks in advance!

[Guges Mk3 226]

You could have left it all stock and dropped in a 40K motor and with your 11.1V You would have reached 28rps easy.

 

But, since you are doing it the old way. I will offer my opinion on your questions.

 

You are not running double bearings are you. Spring guide and piston head.

 

M100 you should not PE.

M110 you will not PE

 

You will not reach 375fps unless you use the M110 spring.

 

Short stroking is not modifying the gears. Its modifying the piston.

 

Short stroking "causes" no issues. You will "use less of the cylinder volume" Nor will it cause engagement issues if you only remove a "few" teeth.

< See video.

What you should do is just drop in a better motor and leave the internals stock, except for perhaps the M110 spring.

[Hangtight 18]

Short answer. Yes it'll commit AEG suicide the first time you pull the trigger.

If you run it on 7.4v then you'll get around 24rps,but you'll be just a little shy of PE. You'll get good trigger response and it'll be reliable.

If you want to run the 11.1v then you'll need the M120, the piston lightened by removing the bearing and replacing it with a light plastic spacer plus a moderate Swiss cheese job. You'll be removing at least 3, probably 4 teeth off the sector gear to drop the fps. You take them off the pick up side of the sector gear so it still releases off the same tooth and doesn't mess up the timing. You will loose cylinder volume, but you'll still have enough for a 250-270mm barrel of you're using 0.28g ammo. That's more than enough for accuracy.

It doesn't matter if you only shoot on semi. A fast set up will likely have overspin so the sector gear will still come round and smash into the piston before it had a chance to complete its stroke.

If you only shoot on semi then for 375fps I'd go with:

SHS HT motor

13:1 gears

7.4v lipo

BTC Chimera (if it fits, but you want a Mosfet that supports pre cocking)

M105 spring

Cylinder ported to suit your barrel length

ICS POM piston and piston head are the business. Keep it.

SHS cylinder head and O ring nozzle are cheap and reliable, if they fit. If not the ICS stuff is OK.

16awg wiring and Deans connectors.

Decent shim work and angle of engagement adjusted correctly.

With 30-40ms of pre engagement you'll get P* like trigger response, and you'll be able to spam the trigger as fast as you like without the motor getting warm, let alone hot. But it'll still deliver a solid 22-24rps in full auto, no PE, no feeding issues.

[jaykim99 1]

I believe this is the piston and piston head that comes stock. (http://www.evike.com/products/54270/). Either of you know whether it comes w bearings?

[jaykim99 1]

Actually I think it does have bearings. Any tips on removing the piston head? There is no screw on the outside and there seems to be a square nut inside.

[Hangtight 18]

If it's like the ones I buy then there should be a Philips cross head screw central inside holding the head on. The screw will be hard to undo as it is fitted with Loctite, so make sure you use the correct screwdriver.

 

These are the spacers :

 

http://m.ebay.co.uk/itm/331684716193?_mwBanner=1

 

You want the 15mm outside diameter by 5mm thick. You'll have to drill out the inside to the right size to fit the top hat shaped piece of metal that holds the original bearing in place. This will save you around 3 grams, and you should be able to loose another 2 grams with the Swiss cheese job. Don't just drill holes at random.

[Guges Mk3 226]

You can tell if it has bearing by looking into the piston body.