overspin causing fps drop, please help

[Crude Skinny B]

Right ok got a G&G Combat Machine AEG GR16 A2 and the stock compression sucks.

so i wanted to turn it into a silent DMR I'm using:
G&G standard gears
shs full tooth piston
pom head
o ring nozzle
shs ht motor/standard G&G
element m110
7.4 5000mah 40c
mosfet

when using the standard motor i get about 304 fps which is still bad for an m110, however when using a SHS HT motor my bb just fall out the barrel, so theres my problem.

As a dmr i need the quick trigger response so i am wanting to use the HT motor.

Anything that you can suggest that i can do to sort this? at the moment all i have left to do is shave some of the front off the tappet plate to sit it further forward.

I do have an ab fet but i rather not use it due to it heating up when using the HT and 7.4 lipo but if the problem is not sorted by sunday i will have to use it.

My end result will be me changing the piston head for a custom one i have made that has an air brake in it, my first prototype made the gun silent really quite surprised, but i want the gun running properly before i implement it.

cheers

[HuntR]

Re: overspin causing fps drop, please help

Sounds like your cut off lever isn't doing it's job effectively. Make sure it can move freely, and it's not worn.

Mosfets will get hot. So i wouldn't worry too much about that unless it's getting steaming hot.

The 110 spring should be getting you at least 350. Check the 0-ring on the piston head. Too make it a better fit you can take it off and stretch it over the cylinder and heat it up a little bit.

As for your airbrake piston head, it will make it an awful lot quieter. However it will reduce your FPS a little. So i'd first try to fix the air leak before utilising that.

[Crude Skinny B]

Re: overspin causing fps drop, please help

the seal in the gearbox is good i can't push the piston in with the nozzle extended so thats fine.

the cut off leaver i shall have a look at and compare it some others.

when i hold hop unit to where it would sit on the gearbox and i block both the barrel and feeding nozzle when i push in the piston at this stage the air comes right out from within the hop unit, anything i can do about this?

yeah with the air brake i wanted the system shooting at an consistent fps before i put it in then i can gauge how long the air brake needs to be.
edit i did a search and the problem is very similar to this one
http://www.zeroin.co.uk/showthread.p...light=overspin

cheers

[North West Outpost]

Re: overspin causing fps drop, please help

It may be your hop rubber and nozzle dont meet as they should.

There is a mod that will give possibly another 0.5mm which could be all you need.

Tappet plate spring??

[North West Outpost]

Re: overspin causing fps drop, please help

Have I understood this wrongly?

Do you get single shot using the shs and monster batt. OR

Single shot then so much over run that it cycles and sort of fires again but doesnt cycle fully. Just enough to allow a bb to be fed in and dribble out.

If it is the latter you need to change the way you have your gun set up. To compensate for the speed of the motor.

We have built that monster HK53 which doesnt have an AB fet and there is no over run on that even with a 14.8.

[Crude Skinny B]

Re: overspin causing fps drop, please help

Care to elaborate on the setup, would be most helpful as I need it setup for sunday

[Crude Skinny B]

Re: overspin causing fps drop, please help

ok guys me and a mate spent all afternoon working on it and now with an m110 we are getting 340 fps so thats good.

the mods that we did were:
sanding down the front of tappet plate, also as we sanded it down quite a bit i had to glue on the nozzle.
we also installed my diy ab fet and to my surprise it did not blow up and die so thats solved the over spin issue (i think).

the only thing that i can see now is that the nozzle is always partially retracted and never stays out in the extended position.

so now i am going to bump up the fps to hopefully 380 using spacers and then install and tune my diy
air brake to bring it down to 340.

all is then left from there is a nice reshim and correct the aoe as i noticed it was slightly off.

thanks

[Lee 303]

Re: overspin causing fps drop, please help

If you want more FPS then fit a different spring
The problem with spacers it that the spring can get Coil Bound before the piston has fully retracted

[North West Outpost]

Re: overspin causing fps drop, please help

If its a long V2 thats about right...They can be troublesome little beggers...lol. Without the psg type springs.

Next time you sand the tappet plate do it on the lower half only and not to make it too thin..

[North West Outpost]

Re: overspin causing fps drop, please help

If you want more FPS then fit a different spring
The problem with spacers it that the spring can get Coil Bound before the piston has fully retracted

You have roughly 18mm of space with a fully compressed spring in a normal gear box in an elongated one that would be arround 40+ with a short spring...lol.

Spacers are a good way of fine tuning fps.

You will soon find out if you have to many spacers. Either it will jam or you will rip the back off your piston.

[thekonassure]

Re: overspin causing fps drop, please help

Or just get a long spring ?