Issues after upgrade

[Mustacheod_Matador]

I have a front-wired G&G M4 Carbine Combat Machine that I bought new. Recently, I added a prometheus 6.03 inner barrel (380mm) and it ran just fine afterwards (I also put in the prometheus 50 degree/purple bucking). 
 

However, after adding an M120 spring, it will not fire with a mag inserted. Without a mag, it dry fires just fine. When the mag is inserted, it sounds like the battery is dying and immediately jams before getting anything down range. 
 

Any ideas on what it could be?

Edited February 20, 2023 by Mustacheod_Matador

[Nick G]

Just going to ask where in the world you are based ? 'cos an M120 spring will take you way over UK power limits for a gun capable of full auto . What battery are you using ?

Edited February 20, 2023 by Nick G

[Mustacheod_Matador]

I don’t play on public fields. Just private with my family. The gun was so underpowered with stock parts. 

I use a standard 9.6V battery that I originally bought with it.

[Nick G]

17 minutes ago, Mustacheod_Matador said:

I don’t play on public fields. Just private with my family. The gun was so underpowered with stock parts. 

I use a standard 9.6V battery that I originally bought with it.

Doesn't matter if you play at sites or just in your garden. If you have a RIF capable of full auto firing that is producing over 1.3j you are technically in posession of a section 5 firearm. Whilst plod is unlikely to come knocking and do checks It can happen. You don't need a a charge of a firearms offence, and neither tbh does the sport.

Stick an M100 spring in that will get you to a decent power level and should keep you legal. Will also put less stress on the gearbox and battery. 

You might try it on a lipo to see if that improves the locking up, does it do it with different mags ?

Define underpowered ? these usually come out of the box at about 1j which is plenty for the garden tbh. If it's lacking range have you adjusted the hop ? I know you replaced the rubber.

Edited February 20, 2023 by Nick G

[Tackle]

33 minutes ago, Mustacheod_Matador said:

I don’t play on public fields. 

What country are you in ? 

[Nick G]

4 minutes ago, Tackle said:

What country are you in ? 

I took it from the answer that he is in the UK 

Edited February 20, 2023 by Nick G

[Tackle]

16 minutes ago, Nick G said:

I took it from the answer that he is in the UK 

LOL sorry Nick, I didn't spot you'd asked the same question, it was the mention of "fields" that caught my eye, in the UK we generally term them sites etc, fields tends to be USA ? 

[Nick G]

25 minutes ago, Tackle said:

LOL sorry Nick, I didn't spot you'd asked the same question, it was the mention of "fields" that caught my eye, in the UK we generally term them sites etc, fields tends to be USA ? 

Lol I miss stuff all the time 🤣Very true, and if the OP is in the USA then not an issue (state dependant probably) 

[Mustacheod_Matador]

1 hour ago, Nick G said:

I took it from the answer that he is in the UK 

Apologies! Didn’t understand the implication of the original question. I am in the US. This form seems the most active, which is why I ended up here. Reddit didn’t provide any answers. 
 

To answer your other questions, I’ve tried it with multiple mags from different manufacturers and it comes out the same. It will not put any bbs through the barrel. It’ll just jam the first one. Is it my motor that needs to be replaced to keep up with the M120? 
If the gearbox wasn’t such a booger to reassemble, I’d just pop the old spring back in at this point. 

Really appreciate the responses!

[Nick G]

No worries, completely disregard the whole 1.3j limit thing lol.  If the BB is jamming in the hop unit it might be that you have too much hop wound on , I had exactly that issue with an M249 yesterday, try taking some hop off and see if that helps. Otherwise it could be an issue with the BB's themselves , some are much better than others . Just to clarify was it shooting fine with the new barrel and hop rubber before the spring change ?

When firing without a mag in can you see the nozzle moving backwards and forwards if you look down the magwell ?

Edited February 20, 2023 by Nick G

[JVacation]

When it is jammed is the bucking caught in anyway? 

 

Does the bb stay in the barrel/hop up until you 'un jam' it?

[Mustacheod_Matador]

5 minutes ago, JVacation said:

When it is jammed is the bucking caught in anyway? 

 

Does the bb stay in the barrel/hop up until you 'un jam' it?

I’ll check that! 
Yeah, when I clear it, I have to wiggle the gun to get it to eject the BB from the mag slot. I can usually see the BB sitting there when I eject the mag and look inside. How would I fix that? 

9 hours ago, Nick G said:

No worries, completely disregard the whole 1.3j limit thing lol.  If the BB is jamming in the hop unit it might be that you have too much hop wound on , I had exactly that issue with an M249 yesterday, try taking some hop off and see if that helps. Otherwise it could be an issue with the BB's themselves , some are much better than others . Just to clarify was it shooting fine with the new barrel and hop rubber before the spring change ?

When firing without a mag in can you see the nozzle moving backwards and forwards if you look down the magwell ?

I appreciate that! I wasn’t sure what 1.3j even meant lol

 

I played with the hop up and it sounds better, but still jamming. It was working fine before messing with the spring.

I ejected the mag and could see the nozzle moving forward just fine. Perhaps the new bucking is the culprit here? May have caused an issue when I reassembled it

 

the attached video is the sound it makes with the magazine in. Nothing is coming out of the barrel, and bbs pour out when I eject. I’m using biodegradable bbs, but I’ve also used these before modifications without issue. 

[Skara]

Following your description (gun works fine without a mag inserted) I'd argue it's a fitment issue, disassemble and reassemble the gun in this order:

 

Disassembly:

Remove upper receiver, mag release, flora pin (small pin above the trigger), rear pin, pistol grip, stock screw, gearbox.

 

Reassembly:

Gearbox inside the receiver, install rear pin, flora pin, mag catch, upper receiver and front pin, stock, pistol grip. In this order, so that you mitigate any possible misalignment of parts and stuff.

[Mustacheod_Matador]

5 hours ago, Skara said:

Following your description (gun works fine without a mag inserted) I'd argue it's a fitment issue, disassemble and reassemble the gun in this order:

 

Disassembly:

Remove upper receiver, mag release, flora pin (small pin above the trigger), rear pin, pistol grip, stock screw, gearbox.

 

Reassembly:

Gearbox inside the receiver, install rear pin, flora pin, mag catch, upper receiver and front pin, stock, pistol grip. In this order, so that you mitigate any possible misalignment of parts and stuff.

Disassembled and reassembled the way you described. I was able to position the wire much better, but still had the same issue. I then took out the new bucking that I installed and put in my stock bucking. It actually fires now, but inconsistently. I’m going to charge all of my batteries and see if that is a potential new issue. At this point, I’m wondering if I installed the new spring backwards. I was so eager to get that gearbox back together after 2 hours of finagling that it’s possible I put it in wrong 😑 

[Nick G]

Shouldn't matter much which way round the main spring is tbh. Might have a very slight affect on fps but should not cause feeding issues. 

 

Did you check the compression iwhen you had the gearbox apart ?

 

 

[Skara]

I suspect the gearbox somehow gets pushed out of alignment by the magazine, which might explain the failure to feed and the horrible noise.

 

Try this quick test:

Remove the upper receiver, score a little mark on the side of the gearbox where it meets the lower, then insert a magazine and see if the box moves.

[Mustacheod_Matador]

On 22/02/2023 at 12:41, Nick G said:

Shouldn't matter much which way round the main spring is tbh. Might have a very slight affect on fps but should not cause feeding issues. 

 

Did you check the compression iwhen you had the gearbox apart ?

 

 

It was extremely hard to keep it compressed when I put the gearbox back together, so the spring was definitely compressed. This makes me feel a bit better since I am not super eager about taking it apart again lol

On 22/02/2023 at 17:24, Skara said:

I suspect the gearbox somehow gets pushed out of alignment by the magazine, which might explain the failure to feed and the horrible noise.

 

Try this quick test:

Remove the upper receiver, score a little mark on the side of the gearbox where it meets the lower, then insert a magazine and see if the box moves.

Okay I’ll give this a shot! I’ve noticed it’s a bit finicky to put the upper back on the lower because of the battery wire (front wired). I finally got it to fit right without the wire being compressed too much. After replacing the bucking, I’m having a slightly better result, but still inconsistency with fire rate and inevitable jamming. I think my next step may be bringing it into a shop and having an actual professional work it