Skara

Blue cylinder is the stock one, the brass comes from my old ICS M4..

Brass one is say 48mm to front of cylinder

Blue is about 45mm to front of cylinder

either would do - not much in it tbh

When you lost say 25fps/0.2j (depending on bb used)

that could have been from refitting bucking/barrel

or in a new hop/barrel setup

or

the bucking refitted to longer barrel that may not have sealed so perfectly

Coz a longer barrel would lean to more creep not less

So I'm a little surprised it drop a bit, should have crept up slightly

which I wonder if the new barrel/hop was fitted 101% perfectly

or a new hop/rubber/nub installed made the difference over original

in other words - if fitted correctly or a new bucking/refitting made a less effective seal or either a bit of dirt/grease ensured a bit more hop required to lift bb and that was where the drop took place

coz all things being equal you should have gained say 0.1j perhaps

The blue G&G cylinder is slung in most G&G's up to say 333mm barrel

and I'd lay money the spring is a m110 (360fps) or just over to make a firehawk type barrel hit 320fps with a 140mm barrel

by all means test/try the other cylinder but something changed when barrel/hop got refitted imho

also if open it up - check compression coz G&G's on some piston heads produce a below par seal, so get good compression with what cylinder seems to seal best on piston, with a decent o-ring etc....

But reckon the refitting of barrel & bucking especially did not go so perfectly and thus you lost power is a possible thing to investigate

or hop unit is sloppy and shifts forward at times losing seal

so ensure spring on hop unit to push it back to seal, if the mag tries to shift it away from box when inserted

something ain't right & whatever it is up with hop/bucking

THAT is what might have caused the drop

Thanks for the reply.

I indeed expected an increase in muzzle energy with the longer barrel.

I have already changed the piston head o-ring as the stock one was crap (all mangled and no matter what I did, it would not seal), the hop rubber was a prometheus purple that got replaced with a prometheus blue (flat) and then back to purple because the blue went in another gun.

Now I have a ML MR-Hop AEG rubber with its Omega tensioner, which is noticeably softer than the two prommy rubbers I had previously. Now, when I had the stock 130mm inner, both prommies gave perfect air seal and consistent readings of 0.98/0.99 Joules, compared to the stock G&G blue rubber that had readings all over the place (same thing happened with the G&G green, chrono looked like it was on LSD).

I am pretty sure I have installed the hop/barrel correctly and the spring that pushes the unit against the gearbox is fairly strong (it's the kind that slides over the barrel). Mags are very consistent due to their AK style locking mechanism and overall tight magwell, if they push the hop away from the box they do it in a very consistent way as well, because the readings are pretty much +- 0.6 m/s

I'll chrono with the new rubber tomorrow and see if it has changed anything, then I'll open it up and mess around with the air seal again.

Worst case it'll be a new piston head + o-ring and a softer spring to compensate for the energy output increase.