ICS M4 - using other Outer Barrel and Hand Guard Brand / issues

[Bigload]

Hello,

Base gun is the ICS M4 Tubular, I believe the older gen 2013 Models.

I am trying to install an SPR kit on it;

1. DBOY SPR KIt / Outer barrel is completely different than ICS
2. Using ICS Metal Hop Unit - I shaved the wings of the hop unit down a little to slide into the outer barrel


Possible issues:
1. Now the BB's won't feed properly - is it a HOP height issue? Should I try a regular hop unit that's not ICS?

2. Hop unit too far in? The outer barrel have groves for the hop that's deeper in than ICS's, could it be the distance of the hop into the barrel?

ICS HOP


ICS outer barrel


SPR kit

[lurkingknight]

if bbs aren't feeding by gravity when you hold the gun upside down, there is an issue with the nozzle or the hopup rubber being in the way. ICSs have weird nozzle lengths, I've workd on 2 m4s that required the metal hopup unit because the plastic one is shit. And on both guns I had to custom sand/lathe an aluminum shs nozzle down to a specific length and cut a bevel into it for it to feed properly.

If you are trying to mix and match on ics exterior parts on an ics upper, you might be making this issue worse. You are in for a world of suck to figure out where it's not working and try to hack a fix to it. I avoid dealing with ics split gearboxes at all costs because the labor rates for troubleshooting would be insanity.

[Bigload]

I put everything back to stock parts... now encountering the same issues?!

first one or two shots fine, then bb's somehow 'sits'.... blank fires, then double feeds, then more blank fires, until bb's forced out...

something funky!?

[RainyEyes]

Originally Posted by Bigload

I put everything back to stock parts... now encountering the same issues?!

first one or two shots fine, then bb's somehow 'sits'.... blank fires, then double feeds, then more blank fires, until bb's forced out...

something funky!?

Check your hopup rubber. Make sure it's seated properly and that the internal hopup arm isn't engaging the rubber so much as to stop the bb's from exiting the barrel.

First 1-2 shots are OKAY and then the 3rd and 4th might have have got caught on the rubber when the 2nd one reset the position on the arm. Ensure all the screws are on tight where it needs to be. Also ensure the hop-up rubber isn't destroyed as a result of misfeeding previously.

[ox56]

When you put the upper gearbox in did it catch at all or did it sit nicely

[Bigload]

The upper gearbox sits nicely... with both the SPR kit and the OEM unit.

I will take apart the hop again, but I have a feeling it might be the tappet / nozzle? Looks normal..

[lurkingknight]

ics nozzle is longer than most aftermarket nozzles but shorter than the shs aluminum one. The issue seems to be made worse when you go to the metal hopup unit. Put your thumb in front of the barrel and pull the trigger, see if there's air puffing from the hopup feed tube.