SIG 556 upgrade suggestions?

MerryDespot

Hello all

Right - here's the deal. I've just had a chance to field test a recent purchase - a King Arms SIG 556 (with thanks to DefenderDude!).
It's firing at .7 joules - which, though not exactly shoddy, is short of what it could do. So - I'm new to upgrading - DefenderDude has suggested a new piston and spring (the original piston was cut to facilitate an electric blow back system and as this is now disabled it needs a new 'proper' piston). Can anyone recommend parts?

Also - it's a version 3 gearbox I believe - does the stock KA v3 allow for a high speed motor without upgrading/changing the stock gearset?

Help and suggestions greatly appreciated folks.

Leftyflip

I really like the Element clear polycarbonate pistons and Systema Duracon piston heads, I've that set up in all my AEGs and find them great. I'd say the KA could take a high speed motor no problem.

MerryDespot

Lefty, you're a gentleman and a scholar. Thanks!

Leftyflip

MerryDespot wrote: »

Lefty, you're a gentleman and a scholar. Thanks!

Well, I wouldn't say that... But yeah:P
I think MIA have the piston heads for a fiver.

glicster

bump,
merrydespot,did you have any joy upgrading ur sig?

im doing one at d moment,have changed piston,piston head,cylinder head,
gears,new spring(element m105) and hop rubber and it still only fireing at .7j

head set is element silent set and im thinking maybe this could be my problem
coz i think the piston head o ring maybe a bit tight and slowing down the piston,
it looked a bit big and stiff than others i have seen,excuse the pun lol???

another theory i have is that the nozzle is not pushing the bb far enough into
the hop and as a consequence there might be a loss of pressure?ill have to check it later.
one more thing,the nozzle is very long,would this have any effect as the compressed air would have
longer to travel b4 hitting bb.
id like to know if you got yours sorted and how?
if anyone else has any advice id like to hear it.
cheers

glicster

fixed!

MerryDespot

There's a long story behind mine mate ... I'm waiting to get it fixed. Glad yours is alright now though - I've always liked the 556.

glicster

this is my 3rd attempt at getting this to fire at a reasonable fps and in the end
i had to put a spring that would put any other gun over the limit.not the best
solution i know but it has me baffled as to where the air leak is,ive tryed
everything i could think of,
im really thinking its because of the long nozzle why the power is down?
range is good now, allthough it might take the bb a little longer to reach its
target

DeBurca

Putting in a spring with a higher than 1 joule energy rating is not a good solution to a possibly air leak problem
For one the extra energy is used to propel the piston harder/faster into the cylinder head as opposed to propelling the BB downrange
That extra energy has to go/do something else and in most cases it is absorbed by the gearbox shell which can lead to premature failure on the gearbox housing (see photo)

So I would strongly suggest that you cure all and any air leaks post haste
Possible problems areas are piston O-ring, cylinder head O-ring, and air-nozzle
There is one further thing that you could look at and that is the piston itself
Does it slide back and forth freely in the gearbox without the spring fitted and all screws tightened?????????
I have encountered this problem on two occasions and it caused me a lot of headache

glicster

i have tryed everything for leaks and all seem to be good.
the piston moves freely coz i changed the stock o ring which was too tight and i checked it for leaks by covering cylinder head with my finger and pushing piston,no leaks there.
i think myself its the nozzle but i dont know what to do with it????? cant find one on ehobby,maybe there is one but advertised for a different gun but i dont know which one fits it???
i know the possible consequences of my set up but it will pass until i get a nozzle.
anyone got a link for what nozzle i need?