AGM GBB M4 first impression, review forthcoming

AGM M4 Valve leak fix and then destroyed

Postby vv1803 » Mon Aug 03, 2009 10:16 pm

Ryu Arcturian wrote: if you've already got the mag disassembled, collect the o-rings and soak them in silicone oil for 20-30 minutes, and put the mag back together, the thread on Arnies there's at least 5 instances I can think of where this happened, and this was the solution that worked each time.



Thanks. Good idea but I found what my problem was. I fixed it --kind of-- and then I managed to destroy my valve right after.

I disassembled the magazine again and almost lost the spring that's at the top. Spent 5 minutes on the ground looking for it so make sure you work somewhere clean where you can find things if they happen to fly away.

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The two pictures below show the stock valve right out of the magazine (I had Teflon tape from before still on it).

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I used a pair of pliers with tape to softened the edges. As you can see I scraped up the pin end of the valve pretty good. Nothing that will cause problems with performance but taking it in and out too often could permanently deform the end. There is suppose to be a tool to use but I don't have/know where to get one.

On the Philippine airsoft forums I kept coming across people talking about a small o-ring dislodging itself when using propane. The red arrow on the next photo shows which one I'm talking about.

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Upon closer inspection, it was indeed deformed and kinda popped out of its seat. I reseated the o-ring with a fingernail and then used super glue to hold it into place as done by other people. I let it sit as indicated on the bottle of glue. I then filled it up with gas and behold! It worked. The magazine filled up with gas instead of spewing it out the top like before. I managed to shoot off half a magazine running on airduster when i pulled the magazine due to a BB jam. When the magazine came out i noticed a continual trickle of gas hissing out the top. NOOO! So yes, I found the problem and then managed to fix it somewhat. With proper o-rings, this mag would be great.

So here is where I FUBAR my magazine. The magazine was leaking slowly but it was still charged with enough gas for at least another full clip. I managed to hit the lever on top of the mag that releases the pin into the 'closed' position through contact with the bottom of the magazine well and also press the pin in slightly with my finger (Everyone says DON'T do this and now I know why). This effectively caused gas to spew out and then cause the pin to out right after. OOooops, I had managed to shear the retaining pin off. The blue arrow in the next photo and the one above will show the difference.

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Without the retaining pin, the upper seal falls off.
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The bronze/brass part becomes useless since there is slack in the system and off it goes.
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Lastly, with nothing to keep it all in place, pop, off that goes too.
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So I now have a busted valve, a face full of bitterant and a very bad start to airsofting. My question, are there any replacement valves out there that you recommend to replace this or would buying a new magazine (probably not AGM) a better option? Are there any magazines that don't have this loose o-ring issue in the first place?
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Postby Pulsipher » Tue Aug 04, 2009 5:53 am

i have heard great things about ghk mags
http://www.airsoftpost.com/magazine-wes ... 31064.html
not cheap though
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Postby Ryu Arcturian » Wed Aug 05, 2009 2:03 pm

I hear the GHK mags are the way to go too.

Update, my bolt broke. As predicted by the thread on Arnies, I distinctly remember at least a dozen people with the same issue, I'll try to get pics tomorrow. I've been really busy with work so I haven't been able to get the review up yet, but its coming along well.

In short the breakage is on the rear of the bolt, most likely from the impact stress coming from firing. Cheap plastic. My plan is to replace the entire Bolt Carrier Group with the NPAS system from Ra-Tech, it might cost more than the gun ($260 :x ) , but adjustable FPS is just freakin cool. I've been reading good things about the Airsoft Surgeon BCG from Redwolf, so that $70ish option is probably going to be the better way to go for most people. I might end up getting that one instead. Not sure yet. Will update later.
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Postby Danger Corp. » Wed Aug 05, 2009 3:52 pm

update with mine:

so far so good! my only complaint is that sometimes when firing on full auto it will jam, b but that may just be a lube problem, i don't know. but so far my bolt is holding up, i too am planning on getting a new one, the one with adjustable fps.
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Postby Ryu Arcturian » Thu Aug 06, 2009 8:33 am

DANGERDOOM64 wrote:update with mine:

so far so good! my only complaint is that sometimes when firing on full auto it will jam, b but that may just be a lube problem, i don't know. but so far my bolt is holding up, i too am planning on getting a new one, the one with adjustable fps.


The double feed is a flaw in the design, both the Western Arms M4 (original model) and the G&G (or G&P I always get them mixed up) have the same feed/jaming issue. You could look at it as added realism, considering that real AR's can suffer a double feed jam also.
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Postby Pulsipher » Thu Aug 06, 2009 11:31 am

Tony are you going to grid 18? i would love to feel up your agm there, dispite any problems it may be having
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Postby Ryu Arcturian » Thu Aug 06, 2009 11:58 am

Most likely yes I'll be going.

I'll be hanging with the gabble of apes and gorillas and shouldn't be that hard to find

Edit: NVM, I have to work :x fml
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Postby Danger Corp. » Thu Aug 06, 2009 3:03 pm

Ryu Arcturian wrote:
DANGERDOOM64 wrote:update with mine:

so far so good! my only complaint is that sometimes when firing on full auto it will jam, b but that may just be a lube problem, i don't know. but so far my bolt is holding up, i too am planning on getting a new one, the one with adjustable fps.


The double feed is a flaw in the design, both the Western Arms M4 (original model) and the G&G (or G&P I always get them mixed up) have the same feed/jaming issue. You could look at it as added realism, considering that real AR's can suffer a double feed jam also.


haha ya i suppose so, good ol' realism
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Postby Ryu Arcturian » Fri Aug 07, 2009 10:23 am

$91.34.... and we thought the AGM was cheap.

http://rsov.com/index.php?target=produc ... ct_id=3804

disclaimer* I in now way endorse this product linked here, I simply thought it worth posting because I'm amazed there's a gbb m4 for under $100. Even though this thing is most likely a complete and total POS.
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Postby vv1803 » Sun Aug 09, 2009 12:21 pm

Ryu Arcturian wrote:$91.34.... and we thought the AGM was cheap.

http://rsov.com/index.php?target=produc ... ct_id=3804

disclaimer* I in now way endorse this product linked here, I simply thought it worth posting because I'm amazed there's a gbb m4 for under $100. Even though this thing is most likely a complete and total POS.



Nice find. Looks like another WA clone. They sell a discharge valve which is also A.C.M brand for the WA M4. I might buy that to replace the one I blew up mentioned above.
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Postby Ryu Arcturian » Mon Aug 10, 2009 8:34 am

It is a WA clone, someone on Arnie's bought it
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Broke it again

Postby vv1803 » Sat Aug 15, 2009 2:47 am

Update: I broke it again...:cry:

I bought 2 new valves for my AGM magazine that i busted and 2 ghk magazines as extras/spares. The ghk magazines require some fitment/wiggling when using for the first time (its tight but it'll fit). I had to shave a bit of material where the hole is for the magazine retaining clip. The magazines are made of an unfinished metal material and work essentially the same way as the original magazine except there is no pin that you can switch on/off for the bolt catch. Filling the magazines is silent and with no leaks around the fill nozzle, however; I still have gas leaking out the exit port but only a very little amount. Just enough to hear a slight pssss sound. Kind of disappointing considering they cost 50 bucks each. Why is it so hard to find any GAS magazines that don't leak?

Continuing on, I replaced the old discharge valve, that blew up on me, with a new one. The new one has a different design that looks sturdier. I lubed the o-rings before installing and reassembling the magazine and i was delighted when it held a charge. YAY!

Ok, so here's where I break it again. After testing both GHK mags and confirmed that they work despite the small leak, I inserted the original magazine with the new valve. After a couple of shots the bolt felt sluggish for some reason like it wasn't getting enough gas. A couple of more shots later and the plastic internals just sheared off and lodged itself in front of the bolt assembly. At the same time the repaired magazine leaks into my face.

Further inspection shows that the new valve lost an o-ring. I'm not sure but that could have been the possible reason why the bolt felt sluggish. Something was jammed in the way!

Anyways, it's time for a new bolt; internal parts and all.
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AGM gbb M4

Postby ghosthands83 » Fri Sep 04, 2009 10:13 am

So after reading all of your posts I'm not scared off yet. The lure of a GBB m4 for 188$ shipped to my door is just too much to resist. I do plan on skirmishing with this gun, though not every weekend and I expect to upgrade it as needed. My only question is at this point! is for replacing the front handguard, is the delta ring real steel spec or is it echo1, TM compatible?
thanks guys
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Re: AGM gbb M4

Postby PanzerFaust » Fri Sep 04, 2009 3:39 pm

ghosthands83 wrote:So after reading all of your posts I'm not scared off yet.


I am.
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Postby Pulsipher » Fri Sep 04, 2009 5:35 pm

FYI
the JG is ALSO a WA clone for 72 bucks before shipping form ehobbyasia
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