G&P M4 Feeding Issues

[bluey6600]

All,

I'm having a nightmare of a job to get a G&P M4 working. It was bought second hand off here and when I got it it was sickly, with the gearbox making noises and BB's not feeding cleanly. I then rebuilt the gearbox, finding out the selector plate was broken (so fixed that), the cylinder head had poor compression (so put Ultimate one in), needed a new piston (so put in SHS piston, bearing piston head and bearing spring guide and systema nozzle). Gears appeared to have been replaced in the past but looked ok. Replaced hob rubber with TM rubber.

So gearbox is now working fine - go to use it and still has feeding issues. Knew about G&G M4 bodies being picky with mags - have velcro at back of magwell to aid in that - but would still be double feeding especially on auto. When testing it it then got really messed up and in clearing it ended up ripping the end off the piston. So second rebuild - this time with G&P piston, and new element high speed gears. Also put in Ultimate tappet plate thinking that could be part of the issue and replaced original G&P metal nozzle

So fired it up this morning - dry firing runs really well, all shimmed nicely. Put a mag onto it - on semi feeds ok at times, with CA hi cap. Beta project mid cap didn't want to play at all. Full auto on the CA hi cap was getting jammed up - either multiple bb's in the barrel, or not feeding any. Before I mess it up more wanted some other advice... know what I am doing on this but this gun is now annoying me.

Options - either all the mags I have don't work on G&P bodies - (Ca hi cap, Dboy hi cap, Beta PMAG mid caps), or the hop unit is somehow messed up on this? Or give up and get a new body and drop the nice gearbox into that! Starting to get really annoyed as thought I had this working!

Surely others with more experience can give advice - thanks!

[mark2191]

Re: G&P M4 Feeding Issues

this might sound daft but is the inner barrel lined up properly? i only ask as i did a custom build a while ago and i was having the same problem, stripped it and put it together multiple times same problem, basically the barrel was not lined up to the hop correctly

[bluey6600]

Re: G&P M4 Feeding Issues

Inner barrel seems to be lined up fine - as evidence by bb's flying straight. I do wonder if this is more of a mag issue than anything - have just tried auto with gun upside down and it definitely fed better.

Recommendations for mags that work with G&P bodies? Or if replace G&P hop with a systema or madbull one is there better feeding?

[Trigger Last Chancer]

What battery are you using , GnPs are rapid as standard so it may be to fast.
The semi issue is standard with GnP the bevel(I think it's called) gear only has 3 notches for the anti reversal latch.
Mag wise 120 e/p mags worked well in mine

[r6shooter]

Re: G&P M4 Feeding Issues

firstly, with the gun upside down mate and unloaded, look down the hop unit and fire the gun on semi, you will see the air nozzle moving backwards and reset, try and watch it to see how much it protrudes by.

if it does protrude, install a sector gear delay chip, will make the timing on the air nozzle correct again and allow the full hole to be open on the hop unit loading channel

also are you sure the air nozzle is a m4 variant as the mp5 one like neon the same bar the length

secondly, if all the above is correct and sorted , insert the mag, fully wind a high cap, and un wind the hop fully, hold the gun by the mag well and push the bottom of the mag forwards so it aligns the hop unit feed channel with the mag lip perfectly

if this doesnt work mate, have a test fit of the hop unit and each mag while the gun is apart to see if seats snuggly or loosely ( ideally loosely so ensures smooth and quick channel location to allow bbs to flow upwards )

[bluey6600]

Re: G&P M4 Feeding Issues

Ok, now taken the advice on here. From the upside down checking and some bb's in the hop without a magazine it is not feeding - it looks like the air nozzle is protruding slightly which is preventing the smooth feeding.

I am 99% sure it is a m4 nozzle on there - I do have another plastic one to change to from the metal one it came with originally. I will also get hold of a sector delay chip as well to see if that makes a difference.

[private parts]

The metal 1s are standard g&p, worth leaving on there

[bluey6600]

Re: G&P M4 Feeding Issues

Well putting the plastic nozzle on there still not feeding. Have tried the hop unit and barrel on another M4 I had (a CA) and shoot and feeds perfectly, so it is the air nozzle that is causing the issues I'm sure. Now have an element delayer chip to put into the gearbox to try and pull the nozzle back another mm or so... Sighs... convinced this gun hates me! lol

[keithhibbert]

Bought an M4 off here and wouldn't feed at all. Tried everything to no avail. Turned out to be a dodgey mag catch. Now feeding great.

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