UMP spring change

Dread-Lock

I have a DE UMP it was bought on RSOV and it was hot. So I bought an M90 spring from Eirsoft to bring it down to sub 1J. Well I can say it does shoot at sub 1J now.....BB's go about 4 meters .

This was my first time taking apart an AEG. I have taken it apart three times now as small things were wrong with it (at first).
-First time the spring on the trigger wasn't in place properly so the trigger just got stuck.
-Second time the timing on the gears was off so BB's wouldn't feed.
-Third time everything went together seamlessly. Or so I thought, but now it just shoot a few meters...

The first two times it was shooting grand, just on the third time it went to hell in a hand basket.
Anyone have any idea what could be causing this? I'm gonna strip it again in the morning, but I just wanna get peoples opinions what might be wrong first.

Oh and I also learned a LOT from taking it apart, so in that aspect it was worth it .

maldondo

Did you re-attach the little spring from the tappet plate to the gear box? Is it feeding ok?

ED E

Yay, UMPs make my day

Yeah, I presume the spring is working ok:p

Whats happening is you are loosing air somewhere. Possible holes:
1. Piston O-ring - If thats missing/damaged you'll have sh1t all sealing inside the piston.
2. Piston head 0-ring - between it and the piston, same as above
3. Seal between air nozzle and piston head. As you know it slides up and down on a small metal tube on the piston head. AFAIK there is a seal on the inside of the nozzle, not 100% though. Also, if its not slotted correctly into the tappet plate below it wont seal with the hop.
4. Following from 3, the hop unit should be pressed tight agains the gearbox. Open the bolt, insert screwdriver and apply small amount of pressure. You shouldnt be able to move the GB, and the hop should be pressed tight against it.

Think thats it pretty much covered.

Stercus Accidit

The air nozzle isn't attached to the tappet plate, or the tappet plate spring isnt engaged.

You'll have to re-do the job.

Dread-Lock

Thanks for your replies guys.

The air nozzle wasn't attached to the tappet plate. But now that I've re-done it, it's not feeding. At all....

Although if I drop a BB down the barrel and fire it fires normally so the power level is back to normal.

What looks like the problem is that the air nozzle is a little to far forward and isn't letting the BB into the hop up unit.
Thanks again for your help, any ideas on how to fix my new problem?

Lethal_Bullet wrote: »

Yay, UMPs make my day

Yeah it's my favourite gun and it saddens me that I have never skirmished her .

Masada

Take out the gearbox and bring it in to me dread, I'll stick it back together for ya and yu can just drop it back in to the receiver.,

Dread-Lock

Masada wrote: »

Take out the gearbox and bring it in to me dread, I'll stick it back together for ya and yu can just drop it back in to the receiver.,

I fecked it up that much huh?? :eek:
Thanks Richie I guess I'll be in tomorrow as I need to pick a few things up for the milsim on Sunday.

Masada

I don't be there on saturday but you can get the lads to bag and tag it, then i can sort it for ya monday.

Dread-Lock

Masada wrote: »

I don't be there on saturday but you can get the lads to bag and tag it, then i can sort it for ya monday.

Grand I'll be out on monday anyway, so I'll drop it in today so that its waiting for ya.

DAMMIT I forgot you guys close early on a Saturday.

Stercus Accidit

Thats a tappet plate issue, the spring may be not on it, or some stupid thing.

Just keep at it, or give it to richie.

Personally, I always keep at these thing til they are fixed, if ye want the gun for tmra thats what I'd do.