G&G UMP speed issue and nozzle length
 

Hello everyone.
I am working on a G&G UMP.
the owner wanted a longer inner barrel installed,
he went to a 363mm Inner and covers it with the Factory suppressor.
but due to the current cylinder being a C type and restricted to inners under 300mm
so i put in a modify non ported cylinder and being the stock cylinder head and nozzle were wuite leaky I put in a Modify dual oring cylinder head.
the stock nozzle still leaks but works better then it did ith the stock cylinder head.

the stock piston head is ported but it leaks a little as well.
now that said, i put in a modify 100 spring with the expectation that the
aeg should shoot in the area of 350 - 370 if it was properly sealed,
with these 2 leaking spot id expect 324 or so.
it averages at 291 but jumps to 600 fps (ya i know there is now way in hell a 100 will give 400 never mind 600.

So i intend to replace the Piston head and Nozzle with modify parts na seal that bastard which will put it in the 350 range..

so all that said i have measured the one in the rifle (assuming its stock) and its longer then a M4, Mp5 and AK nozzles. this one is 22mm (maybe 22.5)

Does anyone know the length of the stock nozzle on a G&G UMP?

this was my gun and i have been talking with Scooter and the new owner of the gun trying to figure out what issues the gun may be having.

Scoot the Modify M100 is good up to 109m/s which is just around 360fps(with an M16 length barrel). 324FPS is 98.78m/s. i have two other guns running Modify M120 that are getting 370-360 FPS (112m/s), it should be getting over 440FPS(135m/s) according to Modify, and i have tested the same spring in another two guns with slightly longer barrels with similar numbers. either Modify is over stating their spring ratings or the 4 guns i tested all have serious sealing issues.

Hi D
to test the modify spring compairison chart, I built an AEG mechbox using mainly parts from the list.
using a Tm m733 body with said mechbox and a Promethus 433mm inner I achieved 375 FPS with the 100.
Chrono and cans M733 style Part 2 - YouTube

as Debriefs aeg is now sporting a 363 madbul running a Similar set up I was expecting 324 with the slight leak from the Piston head (going to change to a high quailty Oring).

Debrief just let me know the nozzle is a modify which explains why it works better with the Modify dual oring Cylinder thats in there now :)

What modify nozzle was in there when you shipped it?
AK, M4??

I red recently that the Modify Sigg nozzle is the closest to a stock G&G UMP nozzle

We still don't know exactly what the factory nozzle length is for a G&G UMP, if anyone could help out :)

363 doesn't = an un-ported cylinder, this could be attributing the to wonky readings.

When's the last time you cleaned out your chrono? Last week every gun I fired through my chrono read 275 FPS no matter what it actually was... When I cleaned everything out there was about 3 BB's worth of shavings in there and it started to read properly.

I'd to the cylinder heat trick to the piston head's O-ring and try to seal up some of the leaking areas and see if that makes a difference.

Anyone?...

looks like a regular G36 nozzle to me, and I would say it's probably your best bet too.
I'm pretty sure I left the stock nozzle in my UMG, I've got calipers here if anyone can bring me a G36 and UMG M4 air nozzle lol

the Owner ordered a Factogry G&G nozzle so I'll post the size once it arrives.
I normally use a non ported Cylinder in anything over 300mm.
then a lighter spring can be used to accompish a similar FPS
versus using a heavy spring in a ported Cylinder.

and with the lighter spring, a higer rof and a entire system taht runs that little bit ezr, batteries last Longer etc.

When i get the nozzle, I'll do the Oring expansion trick, I also have a
couple high quality orings that have a softer rubber and thus seal easier when used with ported piston heads.

and i'll check the Chrono for Dust and Debris Thx

ThunderCactus, if you can tell us how long it is I will have your babies. :)

about 8", real wide too....OH you mean the air nozzle??

Yeah that would be nice and stuff....

lol
If one happens to appear, I can measure it, but I'm gonna say it's most likely the same size as a G36 nozzle. Could be wrong, but at least they're not expensive....
Anyway good nozzles are hard to find anyway, I highly recommend using an ARS cylinder head though, same size as the modify double O-ring head, but always seals better with air nozzles

Yeah, the G36 nozzle seems a little weird to me. There was an AK type nozzle in there before (19mm nozzle) and it was cycling, but it was spewing BBs pretty erratically. Putting a G36 nozzle in would increase the nozzle length by 6mm. I don't know if that would block the feed path, an extra 6mm seems pretty considerable (enough to fit another BB in the chamber).

i figured the same thing, its basically a G36 setup so you would think a G36 nozzle would be the money.

naynay D, the nozzle was 22.5mm which is a Sig nozzle sir.
the only other ak nozzle i have kicking around is a clear plastic from my CYMA.. i dont think that one was in your aeg :)

on a side note, the nozle that was in there is longer then a Mp5, Ak and m4 nozzle. thats when i measured it to find the 22mm to 22.5mm length

teehee teehee
so here is our own Amos Airsoft how to: AEG Compression test - YouTube.
here is a little clip from SV's StoveTop WorkShop -- Failing Compression testing - YouTube,
the only change at this point was i removed the ported cylinder and added the modify M16 non ported

what do you think.. issue?