JG - Jing Gong M4 GBB Rifle

[sear]

I wish I could explain more but I'm basing it on what the user said. When I looked at the picture, I saw a crack just before the front pin below the ejection port.

 

Here's the link: http://www.filairsoft.com/forum/showthread.php?t=83346 , I should've posted this earlier.

[gerrysnaps]

@sear Visited the link. I actually saw that review before I bought the JG, but a couple of things confused me about his assessment, like the supposedly weak hammer spring not being able to run with stronger green gas. I have so far only filled my mag twice with green gas and got 419-440FPS @ 0.20g with green. Going to use up the green gas and try it out with 134A next to see what FPS I can get.

 

As for the front pin I see you mean the front receiver pin. It is held down tight by the retaining pin and I have not yet pulled that out. I'll give it a try tomorrow, at risk of damaging the lower receiver, but I think I'll know what to look out for given the info in the review. It's possible the tightness might cause the plastic housing to break but there could also be other ways one could break a plastic housing.

[Frakk2k]

I finally got to fondle my new JG today. Took some pictures aswell:

 

 

 

(link to page if pictures doesn't work: http://sites.google.com/site/jinggongm4/)

 

The JG feels a lot tighter, the nobs, pins and bolt are all tigher than on the AGM.

Magazine was hell to take apart. The AGM one is easier to pin out, the plastic on the JG mag made it tricky to get all the pins out.

My mag came with some gas in it actually. All the way from china. So I guess it is tight

 

The blowback on the JG feels almost harder than the AGM. A lot more sound. Could be the buffer, it has a hole in it, right where the bolt hits it?

I didn't get around to testing the FPS, but I am guessing they are pretty much the same.

[gerrysnaps]

I finally got to fondle my new JG today. Took some pictures aswell:

...

 

Did you have any problems getting the front receiver pin out? Looks like you managed it without cracking the lower either. It's in tighter than the rear receiver pin so I suppose it might be easy to force out too hard.

Edited September 2, 2009 by gerrysnaps

[sear]

^What's your opinion on the quality of the plastic receivers? I still haven't seen one personally but this looks like an interesting alternative to other GBBs out there

[gerrysnaps]

@sear The material is sturdy enough for starters, but it is still plastic and only millimeters thick, so gotta be careful when pushing the metal pins in by force. Keep checking everything is aligned and you should be fine. I've broken supposedly sturdier Marui plastic receivers by being a hasty dumbass, so it's really more about how careful you are working with it. BTW, front pin removed, no issue cracking the retaining pin housing. As long as you tap it carefully and don't accidentally take a hammer to the receiver you should be fine, at least until you start to want a metal body for it.

 

More observations:

 

Hopup Problem -

There was one new issue I found today trying the hopup for the first time: it was almost completely stuck and would only move a few millimeters in either direction. Brought it back to the dealer to examine this time as it was clearly a manufacturing defect. The other units had the hopup dial working fine. It turned out the plastic for the hopup dial on my unit had some excess material protruding out of it and causing friction on the outer barrel's inner wall. Not a huge problem, just needed to file down the excess and the hopup was all sorted. Can't say yet how many JGs have these sorts of quality issues but whatever their QC process is they seem to miss checking the hopup dial if it actually works.

 

Flashhider and Gas Block -

Probably confirmed by others already, but the flashhider is 14mm CCW/Negative thread so you pretty much have all the options available to you. Instead of a set of washers JG used a rubber o-ring in conjunction with the bottom pin to retain the hider in the alignment of your choice. The triangle sight is retained just like on the AEGs with a couple of pins you can whack out with tools to remove. Changing out the front sight for a different version or even a lower profile gas block can be done without issues as the outer barrel dimensions are the same as on the AEG. The only thing I could not verify was the thickness of the base versus AGM and WA barrels, as I read the thickness has some significance in terms of compatibility with AEG receiver collars.

 

Inner barrel -

The inner barrel is only about CQB length even if the outer is M4A1 length, IIRC the WA and AGM are the same. The barrel is brass, nothing else remarkable to note. This is good in two ways, if you start with an M4A1 base and want a SBR profile you can go to maybe 10.5" without the stock inner barrel sticking out, and if you liek the M4A1 profile and want more than 1.8J on green out of it, you should be able to get more FPS by changing out to a longer inner up to maybe 409mm. I now have a dilemma on my hands as I can't choose between SBR or Afghan profile!

 

Stock tube with Magpul CTR -

Probably already common knowledge, but the Magpul CTR stock drops in just fine on the stock tube with the LE-style end cap. The friction lever helps keep the minimal wobble to almost nothing, but I haven't tried this long term to see how long it lasts after a lot of rounds.

 

Handguard compatibility -

This is a little weird. Basically various AEG handguards could fit the JG with the stock front set but with some modification. I already said the front collar and delta collar are actually a good fit for Magpul MOE handguards versus the AGM, but looking more closely there is still some play when you try to twist it and there is a bit of a gap between the top and bottom handguards. It's not as solid in feel as the stock M4A1 style handguards so one might want to add some material (grip tape, etc) to the ends the delta ring and front collar grab on to make the fit better. I also had trouble fitting both Gen 1 and Gen 2 A&K CQB RIS units on it as the gap between the front collar and the delta collar are just a little off that the groove in the RIS that drops on the teeth of the delta will not line up properly. The stock front collar compared to a Guarder front collar is thicker, so swap it out or file it down to fit a RIS.

 

All in all some minor issues in my book and it's still a good buy to get one started on the GBBR path.

Edited September 2, 2009 by gerrysnaps

[Frakk2k]

The pins was indeed pretty hard, but using a hammer + screwdriver drove it almost out. You don't have to take the pin out entirely either, when the pin is sticking out, just twist the upper downwards, and it will come off. (Something like that). It is the same on my AGM.

 

Plastic body feels sturdy, and thick! I guess it is great if your country has some special rules on this, but othervise I would reccoment metal. For that special feeling you know..

[snorkelman]

WA carbine inner barrel is a shorty, the AGM one isnt (it finishes up around 16mm shy of the muzzle end of the barrel)

[Ion]

Just got my M4, absolutley amazing. Passed my expectations. Yeah, trades are a bit of a letdown.

 

Mag has no leaks!

 

I also do need some help. For some reason after every shot the bolt locks back like its out of ammo. Anyone got any ideas of why this is or what can be done to fix it?

I'll be fiddling with it.

 

Kicks pretty good too!

 

Update: my bolt isn't locking back anymore. It doesn't lock back at the last shot either... Oh well I guess, I was looking inside and it looks like the bolt catch is deformed where it touches the bolt carrier. I think it bent or chunked it up a bit. Oh well, RA tech Steel bolt catch was on the list anyway.

 

I'll update it more as I go.

Edited September 5, 2009 by Ion

[michaelmike]

Found a load of disassembly pics here

http://www.power-dy.com/html/c6/2009-08/2833.htm

Sorry it's in chinese,but if anyone has question as to what a particular picture's accompany text means,copy n paste the pic here,i'll try my best to translate.

 

Cheers.

[gerrysnaps]

Shot with green and 134A today.

 

First shot on green, since the mag was already loaded with it from days before. I started on semi. Recoil was good, shots placed downrange consistently. After about 15 rounds switched to auto, but was expecting the gun not to cycle. To my surprise it cycled and cycled and cycled! Until I ran out of gas and cycling slowed down to the point that BBs were no longer getting fed. Charging it would allow me to get a couple more shots out.

 

Gas completely gone, I switched to 134a. I started on semi. Recoil was noticeably weaker and the bolt was less snappy coming back. Switched to auto and it was sluggish going through it. Ran out of BBs but the bolt did not lock back. Need to inspect the bolt lock to see if it has already worn down, though holding the bolt lock back when charging does keep the bolt open. Don't know if it has anything to do with the fact I'm using 134a this time. Would be disappointing given I've only got maybe 150 rounds through it.

[gerrysnaps]

@Ion does it still lock back when you charge it on an empty mag? Mine still does most of the time.

Edited September 5, 2009 by gerrysnaps

[Ion]

@Ion does it still lock back when you charge it on an empty mag? Mine still does most of the time.

Somtimes, I think the fact that at first my bolt catch got stuck when I first started firing it, so It broke it somehow. Kinda dissapointing. It looks really weird, kinda like when you take a screwdriver to plastic. I can still lock it back manually. I'm positive its the bolt catch, because the mag pushes the bolt catch out still, and sometimes the gun will lock back.

 

But man oh man! This gun is awesome. I was expecting the kick to be a lot less (I figured it was kinda overexagerated on the forums) but no, it does give a nice response, feels pretty real. If I had to compare it to somthing, it would definitly be more than a .22, but I havn't fired a .223/5.56 in a long long time, so no comparison for that. We've got only .22s, .17s, and 7.62s round these parts. Haha.

 

Well worth my money though.

 

Also, my hop-up seems to be working a little too well. It overhops waaaaayyyyy too much, even with .25s. I'm looking into why the hop-up isn't turning very well. Seems like it clicks a lot and is kinda dificult at times to adjust.

Edited September 5, 2009 by Ion

[Ion]

I can't edit my post anymore, it hasn't even been a day yet... Oh well, sorry for the double post guys, I felt that its kinda intresting information.

 

The reason why my bolt catch looks like its plastic thats been chewed up with a screwdriver is exactly that. Its made of plastic. I'm almost sure of it. Kinda weird that they made it out of plastic. So put that on the list for things needed for this gun.

 

On another note, gun is shooting very well still. Mag is great, performance is great. Just need to fix that hop-up. Haha.

 

Also, it has 14mm CCW threads, I put on a Madbull Suppressor today, fit perfectly!

 

EDIT: took the upper off, took the Bolt carrier, and charging handle out. Looks perfect. So far around 400rds fired I believe.

Took a closer look at the bolt catch, there is one part where the bolt carrier comes in contact with the bolt catch, that part is made of plastic, so its made a ramp that the Bolt carrier won't stop on. I may take that plastic off and use the metal part, but I'm not sure how the bolt carrier will fare stopping against metal each time.

Edited September 5, 2009 by Ion

[gerrysnaps]

@Ion Sorry to hear that. I shot some 300 rounds through it total today alternating between semi and full auto, on green gas, and the bolt catch worked without a hitch on semi but consistently failed to stop the bolt on full auto. Perhaps you've been shooting it on full auto all this time?

 

I also realized my green gas bottle is to blame for all the times it failed to fire full auto. It wasn't filling up the mag as much as I thought it was due to a severe leak that I thought was just the seal on the mag but was instead a leak on the can itself. Whenever I made sure to load it with a lot of gas it performed just fine.

[snorkelman]

@Ion Sorry to hear that. I shot some 300 rounds through it total today alternating between semi and full auto, on green gas, and the bolt catch worked without a hitch on semi but consistently failed to stop the bolt on full auto. Perhaps you've been shooting it on full auto all this time?

 

try freshly filling the mag and loading it up with 5 or 6 BBs test bolt lock function

 

repeat same test, ie top mag back up with gas and load with five or 6 BBs again, this time with really rapid semi auto rather than full auto.

 

 

[Ion]

@Ion Sorry to hear that. I shot some 300 rounds through it total today alternating between semi and full auto, on green gas, and the bolt catch worked without a hitch on semi but consistently failed to stop the bolt on full auto. Perhaps you've been shooting it on full auto all this time?

Nope, I've been shooting mostly semi to be honest.

I'm pretty sure it was because at first my bolt was continuing to lock back after every shot for one mag, so I think it wore it down quicker than it should've.

[Ion]

Now my bolt doesn't even stay back when I hold the catch back. Haha. Oh well.

 

So I've been looking into the issue with the gun not firing in full auto at times. Its not that the hammer isn't returning all the way back, its that the trigger at times won't release the hammer in full auto. I took off the upper, put the hammer into the "cocked" position, and selected semi, hammer returned forward as regular since the gun always works in semi. So I "cocked" the hammer, and selected auto, after trying it a few times and pulling the trigger back, sometimes the trigger won't release the hammer.

 

If anyone has any ideas as to why this is, I'm thinking its the trigger but someone with a little more expierience with the WA system might have some insight?

 

On a side note, the full auto not working every time isn't a big issue for me since I pretty much only use semi all the time.

[snorkelman]

with the upper open the trigger should never allow the hammer to be released while you have selector set to auto unless

 

a you cocked the hammer while fireselect was set to semi and then switched selector to auto

 

b you cocked the hammer while selector is in auto and then flicked the hammer lock forwards

 

c you cocked the hammer in auto, switched to semi and back to auto

 

 

reason for all that mlarkey is that when set to auto the hammer lock only releases the hammer to allow it to fire when the bolt carrier is pushing the hammer lock forwards/downwards

 

 

 

auto problems when your rifle is all bolted together

 

if complete rifle fails to fire in auto/ stops firing during an auto burst, what are the symptoms?

 

do you pull the trigger and nothing happens

do you switch to semi and it fires just fine

do you rack the bolt carrier manually and it fires after that?

 

 

could be that the bolt carrier isnt returning fully to battery - even if its just a teeny hairsbreadth off being fully home that will be enough for the hamer lock to fail to disengage

 

if above are the sort of symptoms you've been having then next time the gun fails to fire in auto dont do any of the usual stuff. Instead press the forward assist or see if you can nudge the bolt carrier a teeny wee but forther home with a finger pressed against side of it, then with the selector still in auto try pulling the trigger again.

 

Edited September 27, 2009 by snorkelman

[Ion]

Ah, many thanks for the info!

 

It was the "A" option.

 

I'll just have to keep messing with it to find a solution. I guess I'll try a new hammer spring. But again, its not too big of a deal for me that auto doesn't work all the time.

[snorkelman]

no worries, next time it plays up in auto let me know wether the 'no racking bolt carrier' options above help any and we can take it from there

[Dom S]

Hi guys, Ive just read my way through the topic, and i was looking for a bit of help.

 

I want to get one of these rifles. Im quite happy with the plastic reciever. I intend to be using it on semi only, using 134a gas (to get it to legal uk fps... hopefully...)

 

What fps am i looking at using this gas?

 

Will the bolt lock back on the last round, if im shooting on semi auto?

 

Because im using 134a, im assuming the parts wont wear *too* badly. However, if i said i had £60 or so to do some basic upgrades, what would you reccomend? a steel bolt catch, a new hop chamber.. thats probably £30 odd gone right there. What else really needs doing?

 

With a steel bolt catch, on the pot metal bolt carrier, firing semi on 134a, roughly how many rounds would you guys estimate i would be able to fire before *something* broke? if something was going to break, what would it be?

 

What sort of accuracy will i be getting from this thing, at say, 30 metres, using 134a? i dont need rof or super long range, but trigger response and accuracy are more important.

 

 

I know thats alot of questions, i apologise, and thanks in advance!

 

[Ion]

I went through my bolt catch incredibly quick. I am getting 349fps with .25s and GG. The guns is incredibly well built. The BCG is actually pretty nice. I would reccomend a steel bolt catch, and a new hop-up unit. The bolt catch has a plastic part that gets chewed up by the Bolt carrier. You can remove that plastic piece though. I'm planning on doing that.

 

I wouldn't bet on much breaking if anything. So far mine is holding up.

 

And yes, the bolt locks back every time whether on semi or auto.

[Dom S]

though surely if you put in a steel bolt catch, it is then the bcg that will get worn down, and these cost alot more to replace?

[Ion]

though surely if you put in a steel bolt catch, it is then the bcg that will get worn down, and these cost alot more to replace?

I don't think so, not by a lot, maybe a bit. The Bolt carrier wore out my plastic part on the mag catch simply because the plastic was incredibly soft and the metal of the bolt carrier has a sharp edge on mine.

I think that a steel bolt catch should be fine with the bolt carrier. And I think cheap bolt carriers can be had.