Gg Armament Cm16 Lmg Issues

[RAM]

Hi guys I bought a used G&G Armament CM16 LMG which I chronographed last night and was only shooting at 230fps 0.56 joules and decided to change the spring over to a Element M95 spring which got it to roughly 295fps and 0.9 joules. So decided to have a go at Shimming it and also give it a clean up and check stuff. I found that the cylinder and piston wasn't really holding air pressure properly but I am not sure what Cylinder head and such to replace it with. I did try cleaning the old grease off and applied new grease but it only seems a bit better so I would like to replace the parts.

I understand it is a V2 Gearbox and that it is not a true LMG more of a hybrid but I am not sure if I should buy the LMG Cylinder head or just the regular V2 Cylinder head. 

This is what I was looking at.

https://www.patrolbase.co.uk/asg-ultimate-cylinder-head-lmg-version

 

https://www.patrolbase.co.uk/asg-ultimate-cylinder-head-v2

 

This is what is in there at the moment of it helps.

 

Any advice would be very much appreciated.

[Adolf Hamster]

are you sure the leak is at the cylinder head and not the piston?

 

that looks like a standard m4 type so either of the 2 you link to should work.

 

at the risk of invoking the wrath of negative airsoft you can also patch up the seal of the existing head with ptfe tape.

 

it's worth bearing in mind that the air tube on different brands of cylinder head can be slightly different, so a given cylinder head with a narrower tube can simply move the air leak issue on to the nozzle side if it's not matched with an appropriate nozzle.

[Sitting Duck]

The cylinder head is fine tbh

it can be improved by wrapping some ptfe tape around it

about 3 wraps & trim off excess with scalpel/sharp knife

(yes it is a bodge but it does work well if done neatly,

plus change as little as possible if starting out teching)

 

The main crappy thing is the std G&G piston head

I have never really got great awesome compression with it

 

A good combo is the SHS TT0081

https://www.ebay.co.uk/itm/SHS-15-Tooth-Poly-Piston-Alloy-Head-TT0081-With-O-Ring-Airsoft/353103859892?hash=item5236a150b4:g:Z2kAAOSwRXxe4kEj

 

SHS pistons can bind, be a smidge tight in some boxes but not G&G's

and the head - though alloy which some prefer plastic/POM piston heads...

It is banging as it is - if you don't get good compression the o-ring must be missing

 

It might come with bearings inside, I would consider using the G&G's black spacer & collar

in the SHS alloy head - or apply some mild/blue threadlock to threads if using bearings

 

The piston is a 15 tooth, not a 14 tooth rack, so the 2nd tooth is still there on SHS rack

so really you might need to remove rack & dremmel the 2nd tooth off perhaps

BUT if you don't correct AoE you might just be OK leaving it as is,

though I'd look to remove the 2nd tooth if poss

or just use the alloy SHS piston head on G&G piston if unsure

 

Yes you could buy another piston head, but I have bought a few that were not much better than the G&G

plus for £11 for both say a £10 SHS piston with a nice good compression head for another quid

 

The SHS piston will bind in say Cyma v2 boxes but not in G&G's (tiny bit more room on rails inside)

You could buy a Cyma complete piston, might need to stretch o-ring a bit, but it will be a tiny bit looser in a G&G

So a SHS piston in a G&G box works very nicely imho, and piston head is top notch for compression (honest)

 

As said I'm not a great fan of alloy piston heads, but I know that TT0081 works really well for G&G CM16's

If I could only buy/replace only ONE thing only in a G&G Combat Machine box - that is what I would fit

 

The other thing I'd consider is a bearing spring guide, coz the bearings at back will give you more spring compression

aprox 20fps over the std solid spring guide...

https://www.ebay.co.uk/itm/Rocket-Airsoft-Rotary-Bearing-Spring-Guide-Mechbox-Gearbox-M-Series-bbs/353033134403?epid=25032320745&hash=item52326a2143:g:QOgAAOSw8MpehgWH

 

if you grab this please make sure you select V2 type

 

(sorry Pete you didn't seem to have the piston combo in stock m8)

 

The piston combo will provide great seal/compression (seal cylinder head with ptfe) and get you say 314+fps on m95

the spring guide will give you about 20fps more to say 334fps

 

You could change nozzle, you could change cylinder head too - BUT change as little as possible

that way you minimise any issues like nozzle too long (feed issues)

or even in rare cases some cylinder heads were fatter and box didn't close up 101% (rare but has happened)

 

But as you are perhaps new to this and maybe unaware of the TM compatible BS at times

you don't want to gut it completely and run into potential issues coz 1 part is not quite 101% fully compatible

 

So I've suggested just 1 or perhaps 2 parts to consider changing to gain efficiency

without a big risk of shit not working on your first attempt - hence maybe keep cylinder head nozzle etc...

Keeping it simple & on a very modest budget with just one or two things that will yeild good results

 

you might have to tinker with the 2nd tooth on the 15 tooth rack - but it is a good buy for £11

[Sitting Duck]

35 minutes ago, Adolf Hamster said:

 

at the risk of invoking the wrath of negative airsoft you can also patch up the seal of the existing head with ptfe tape.

 

 

(Luke screams)

 

totally agree with ptfe if done properly & neatly - I still fucking do it

 

G&G cylinder heads are not awesome, needs about 2 or 3 wraps

Cyma cylinder heads just fall out & I mean fall out on there own (need about 6 wraps at least)

 

But I've found it is the G&G piston head - it is just semi shit to meehhhh at best

& I've tried lots of different size o-rings & types like different colour o-rings, black, brown, red

never got great results, even lining it with ptfe inside to push the o-ring out, NOPE little joy

 

Some people have disagreed, but most of the people I chatted to say yeah that ain't all that

 

JG (5 holes) & Cyma piston heads (8 holes) are very good, Cyma's need a stretched/new o-ring though

but G&G std piston heads are a bit wanked imho, I've yet to get really great awesome seal/compression with 'em

 

I think a fair bit of it is to do with the rear of the piston head...

You want a piston head with as large as possible diameter at back, without rubbing on cylinder wall

to provide max solid support to o-ring as it hurtles down the cylinder building compression as it goes

Some piston heads are smaller in diameter at rear, that allows less support and air to lightly slip past

Thus you end up with some compression tests as OK-ish and then some are "fuck me, that's awesome"

Obviously there is the o-ring itself and also the effectiveness of the ports/vents at the front pushing out o-ring

But discovered some piston heads are better than others and a considerable part of that imho is support at back

 

I will nearly always re-use the cyma stock piston head with a M3 bolt & nylon locking nut in a better piston

(or the cyma piston combo, but the piston head seals great with a new o-ring on it)

 

The OP could buy that from Pete...

https://www.ak2m4.co.uk/internal-parts/pistons/cyma-15-tooth-reinforced-piston-piston-head

but it is also a 15 tooth, comes with 9mm spacer that will add more fps

but be a little looser - not too loose btw, in the G&G and work very well too

Just that SHS combo is a good buy too and unlike Cyma boxes, doesn't bind in G&G boxes

(so I'd lean towards the SHS tbh for a G&G box & Cyma combo for say a Cyma box)

 

you could pm Pete and he might be able to sort you out if buying a few bits @ak2m4

but just change a few essential bits than go nutz - yeah we all can get carried away sometimes

just change a couple of things than risk fitting shit that causes more grief than it fixes if possible

[RAM]

Thanks guys for the help I have ordered from ak2m4.co.uk these parts hoping that I can get it working right for this coming Sunday game at Apocalypse.

SHS (RA) M4 Cylinder Head Aluminium (Pad)

SHS (RA) Piston Head (Double O-Ring Aluminium)

Rocket 15 Tooth Piston

[Adolf Hamster]

16 hours ago, Sitting Duck said:

totally agree with ptfe if done properly & neatly - I still fucking do it

 

i do it to me own guns, and i'll do it to me mates guns, but i can see his viewpoint that it's a band-aid for the proper solution of having good o-rings and certainly if i was being paid good money to work on a strangers gun i'd stay away from the ptfe.

 

it's not as egregious as some of the "uses" of ptfe tape out there, most notably people using it as replacement screw threads.....