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
