AGM M4 GBB

[raito]

Check all the orings in your valve.

 

Anybody know how to get to these o-rings? I've never disassemble a gas mag before, I've only disassembled it as far as the mod Luis explained to get the bolt catch working...

[Stealthbomber]

I'm currently working on getting the problem with the BBs rolling out of the barrel solved. I think it has to do with the hop-up.

 

As for recoil, there are several ways to increase it. Personally the stock recoil is weak on propane.

 

To increase felt recoil you can:

 

1) Run it with red gas/Co2

2) Get a heavier buffer(more weight= more energy towards your body)

3) Stiffer buffer spring for snapier recoil

4) Speed buffer spacers

5) Heavier bolt carrier (a combination of an aluminum nozzle and a stee l bolt carrier. You can even add a bit of weight to the back of the BCG.)

6) Polish the bolt and the inside of the upper reciever to let the bolt carrier glide smoother and faster.

 

I think that's it. Since the gun isn't using gunpowder, were kinda limited to what we can use.....

 

-Luis

I disagree with most of that, as do the majority of other people.

 

The gun is designed to work with 134a. People use it with propane and there are problems as a result. Red gas is ASKING for shrapnel wounds and a broken gun IMO.

 

A heavier buffer and stronger (or pre-tensioned - that's "spacers" to you) buffer spring will absorb more recoil so the shooter feels less.

 

Personally, I think people should learn to enjoy the recoil as it is rather than trying to make it more and more violent. In the end, all you're gonna do is cause damage to your gun due to the extra shock.

 

Anybody know how to get to these o-rings? I've never disassemble a gas mag before, I've only disassembled it as far as the mod Luis explained to get the bolt catch working...

 

To get to the gas release valve you need to remove the valve housing from the top of the mag.

Another kinda half-a*sed bit of design there, IMO.

 

Not sure if it's the same on the new mags (I think I read that they have less pins) but on the original mag you need to remove the 4 small pins (#214) from the front of the mag and the BB cover (#202) which'll allow the mag spring to, erm, spring out.

You then need to knock out the roll-pin (#213) at the back of the mag just underneath the cut-out for the mag catch and another pin on the front of the mag (#215).

 

With that done you can wriggle the valve housing out of the top of the mag.

Note that there's a tiny spring (#224) under the gas lock lever (#211) and there's also the 2-part bolt catch lever (#204, #205).

All these bits can fall out as you remove the valve housing. Collect em up for replacement.

 

You can now use a suitable tool (or pliers) to unscrew the gas release valve and inspect the o-rings.

 

I gotta say, disassembly of the mag has already been covered (with pictures) in this thread, 0n page 33, so it might be better to browse more before asking the same questions over and over.

[the hot tuna]

I was dead set on getting a WE, but after reading every thread on the WE and everyone on the AGM, I've decided to go with the AGM!

 

thanks to all and to all a good fight(will plastic bb's)

 

-Holt

[Luis21]

I disagree with most of that, as do the majority of other people.

 

The gun is designed to work with 134a. People use it with propane and there are problems as a result. Red gas is ASKING for shrapnel wounds and a broken gun IMO.

 

A heavier buffer and stronger (or pre-tensioned - that's "spacers" to you) buffer spring will absorb more recoil so the shooter feels less.

 

Personally, I think people should learn to enjoy the recoil as it is rather than trying to make it more and more violent. In the end, all you're gonna do is cause damage to your gun due to the extra shock.

 

I've personally used both duster/HFC134a and propane/green gas with the gun.

 

Duster/HFC134a:

 

- Slow rate of fire on full auto

- Lower FPS

- Less stress on bolt(plastic bolt that transfers the gas into the barrel) due to lower pressure

- Extreme magazine cooldown during rapid firing(semi double taps and full auto)

 

Propane/Green Gas:

 

-Nice rate of fire on full auto

- Higher FPS

- Higher stress on bolt(look above) due to higher pressure

- Less magazine cooldown, even during rapid firing(better for skirmishing)

 

Both:

 

-BBs roll out of barrel

-Recoil is basically the same; no significant difference

 

Whatever you use, it's basically the same. From what I've seen duster is use less in my opinion, unless you're required the lower FPS. Duster is slugish and cools down way faster than propane. I don't use it and see my duster purchase as obsolete.

 

Red gas wouldn't blow up the gun. It'll wear the gas chamber down faster and maybe cause a leak in your magazine but the man asked what he could do to increase the felt recoil, so I answered.

 

Red gas would be one of the easier ways to increase felt recoil.

 

There's no need to do what I recommended, they're only suggestions, do them at your discretion.

 

And yes I mixed up things a little, thanks for clearing that up.

 

Anyways, I cleaned the barrel, cleaned the hop-up chamber, stretched the little hop-up spring and washed the oil off the bucking.

 

I did this because I thought the cause of the BBs rolling out of the barrel was because the hop-up rubber wasn't getting a grip on them and just letting them slip by.

 

I did this and the BBs kept rolling out of the barel when pointed downwards. I'm thinking this has to do with the bucking, the little nub that puts pressure on the BBs is too short, it doesn't go down enough to pressure the BBs. Even when the hop-up is fully on.

 

I have to do more testing and find a way to get the hop-up arm to push down harder. My gun would now be perfect if it wasn't for the BBs rolling out of the barrel.

 

Happy Fourth everyone!

 

-Luis

[Badly Browned]

FWIW, I don't have the problem with BBs rolling down the barrel. My hop up rubber has that masking tape around it as well.

Edited July 4, 2009 by Badly Browned

[Rob15]

Are you sure red gas is such a good idea?

 

If mags are leaking on green they'll leak like mad on red gas, if they hold green ok its possible red gas could push them a bit far and cause them to leak.

 

Also with reports of mags swelling up with green gas i'd be concerned about the safety of red gas and the potential for them to explode.

 

Not to mention the most important point (sort of), red gas is usually much more expensive than green gas or propane, in the UK its nearly double the price of a can of green gas and about 6x the cost of propane!

[Stealthbomber]

Are you sure the nozzle is physically pushing the BBs through the hop-up?

 

Here's a thought (in case you haven't tried it yet)...

Whip the stock and buffer tube off.

Load a mag with a few BBs (but no gas) in it.

Use the charging handle to pull the bolt carrier back.

Now use summat like a screwdriver through the back of the receiver to push the bolt carrier forward SLOWLY again.

Do the BBs still roll out?

Now try the same thing again but give the bolt carrier a good shove forward.

Does it happen now?

 

If it happens all the time you can be pretty sure it's because the nozzle is too long.

If it only happens when you slam the bolt carrier forward then it might be the shock that's doing it.

If you can't get it to happen at all then the problem might be more to do with what the gas is doing inside the gun rather than something mechanical.

 

*EDIT*

On the subject of Red Gas, I should say that the pins holding the top on my mag are bent every time I remove them.

That's happened after using the mag for a couple of weeks with green gas.

If one of those pins bends slightly further it'll pull through the walls of the mag and the valve housing could fly out.

I think I'd want to be fitting new pins before trying red gas in the mag.

 

And body armour.

[morb]

been through my first skirm day with it.

I've used dustergas and i'm not happy with it at all. Gas consumption seems to suck.. don't know why though. sluggish cycling, etc..

Mags that suddenly vented all their gas on the first shot (GHK mags)

Then i used Ultra gas. (a bit lighter then green) and it was performing great, steady shots, proper cycling. Good gas consumption..

 

Therefore i've come to the conclusion i'll have to get the npas from RA-tech. Belgian fields are limited to 350 fps, will the gun cycle/run the same with npas and ultra/green gas as just the stock gun on Ultra/green gas?

[ruchik]

I have tried again and again to get that tiny o-ring on the valve shaft that keeps unseating to stay put, with no success. I've tried bigger o-rings, they don't fit in underneath/behind the brass plug on the end of the valve shaft. I broke the o-ring by accident, so I tried wrapping everything in teflon tape tape. That didn't work either. Then I cannibalized the fill valve o-ring from another GBB mag, which fit perfectly. Wrapped some teflon tape around that, that works for about half a mag then started venting gas again. I am at my wits end with this. Is there some trick I'm missing to keep that damn thing seated?

[Luis21]

@ Badly Browned: My hop-up didn't come with the masking tape stock, I might have to give that a try.

 

@ Rob 15: My mags don't leak at all when filled with green gas/propane. Only try red gas if you want more blowback or FPS and your magazine doesn't leak on green gas/propane.

 

@ Stealth: When ever I chamber a BB manually and put the charging handle forward into the chamber slowly the BB doesn't roll out. However when I rack the handle and let it go, the BBs roll out, same with firing. The nozzle isn't too long.

 

The poblem is that the hop-up doesn't grip the BBs good enough to hold them there. I need more downward pressure from the hop-up arm.

 

@Morb: Yes, duster is horrible. Bad gas consumption too due to the terrible cooldown of the mags. Duster cools down alot, even in the 80 degree F weather I was shooting in yester day. Use propane with an NPAS or MDK Marshal's valve mod.

 

@ Ruchik: Sounds like you're having a terrible time with that magazine. What was the initial problem again?

 

I'll be out most of the day but I might get back to work on the hop-up later or tommorrow.

 

Thanks guys,

 

-Luis

Edited July 4, 2009 by Luis21

[snorkelman]

been through my first skirm day with it.

I've used dustergas and i'm not happy with it at all. Gas consumption seems to suck.. don't know why though. sluggish cycling, etc..

Mags that suddenly vented all their gas on the first shot (GHK mags)

Then i used Ultra gas. (a bit lighter then green) and it was performing great, steady shots, proper cycling. Good gas consumption..

 

Therefore i've come to the conclusion i'll have to get the npas from RA-tech. Belgian fields are limited to 350 fps, will the gun cycle/run the same with npas and ultra/green gas as just the stock gun on Ultra/green gas?

 

yep no difference other than the reduceable FPS at muzzle end of the gun

 

if you layout 260 for the entire variable NPAs bolt carrier assembly you'll get a bit more felt recoil (or maybe more accurately more felt 'bolt slam' as it returns to battery),

 

if you want better value option then just buy the NPAS bolt fit it to the AGM nozzle tube and shove it back inside the AGM bolt carrier $60

[Cephas]

@ Luis, the issue maybe be your hop up. But what is sounds like to me is that the bbs from the force of the bolt returning to battery are being pushed past the chamber section into the hop up. You could increase your hopup but I imagine at some point those bbs will start sailing upwards. Maybe you could reduce nozzle length a milimeter so the rubber hopup chamber catches it.

[Luis21]

@ Luis, the issue maybe be your hop up. But what is sounds like to me is that the bbs from the force of the bolt returning to battery are being pushed past the chamber section into the hop up. You could increase your hopup but I imagine at some point those bbs will start sailing upwards. Maybe you could reduce nozzle length a milimeter so the rubber hopup chamber catches it.

 

Yes master.

 

-Luis

[Rob15]

@ Rob 15: My mags don't leak at all when filled with green gas/propane. Only try red gas if you want more blowback or FPS and your magazine doesn't leak on green gas/propane.

Green gas has a pressure of about 120psi at room temperature if i remember rightly, Red gas has a pressure of about 150psi again if i remember rightly.

 

If your mags don't leak on green it doesn't mean they won't on red gas, its higher pressure so there is a chance the mags will start leaking regardless of what they do with green gas in. Saying they'll be fine if they don't leak with green gas is like saying mags that hold 134a without leaking will be fine on green, not always true...

[jonny2400]

Guys

 

Firstly, after using my AGM with the MKII mags all day and doing the mag well mod, to allow easy removal. I have noticed that the MKI seem to swell a lot more than the MKII.

 

Any one please please please... point me in the right direction on how to remove the hop up. Am stuck with this one!

 

Next I have noticed that my Stock white plastic bolt has cracked at the rear, when i pulled it out, I found the bottom park has a nasty crack. Now it may have always been like that, as it still works fine. But I am quessing I should get a replacement. Any sugguestions

 

Also Like other guys mention my hop up, it pants the BB roll out... and also the hop up makes no different, no matter if it is turned up or down.

Edited July 5, 2009 by jonny2400

[Stealthbomber]

To remove the hop-up you need to separate the barrel from the receiver which means unscrewing the barrel nut.

 

You'll either need water-pump pliers or a proper tool to do this... assuming it isn't already loose. Most of em seem to BE loose out of the factory.

 

The hop-up actually lives in a tiny space at the front of the receiver.

When you remove the front end the hop-up and inner barrel will come away from the receiver at the same time.

You MUST keep an eye open for the tiny little spring which lives in the hop-up unit. As you slide the hop-up away from the receiver it's free to spring its way to freedom unless you grab it.

To be fair, it's not usually under a lot of tension and you can minimise the apring tension by winding the hop-up all the way on.

 

Once you've got the hop-up out of the gun you need to give it a good check over. Mine was built totally wrong and yours could be as well.

[ruchik]

The problem was that the o-ring on the valve shaft kept coming unseated. I can't get it to stay put no matter what I try.

[Guinness]

LOL

 

I've read a couple peoples reviews/comments- "Spring twangs in the stock tube" and that is listed as a 'negative'

 

 

obviously you've never shot a real M16..... That's one of the 'trademark' characteristics

[morb]

The problem was that the o-ring on the valve shaft kept coming unseated. I can't get it to stay put no matter what I try.

 

 

I have the same problem with my AGM mag, I've done the same mods as you with first some teflon around it, o-ring on it, etc... nothing seems to work, it always seem to get stuck again after a few shots.

I think the only solution is to get a proper o-ring..

 

I'm fearing for the other 2 AGM mags which are on their way... oh well my GHK mags seem to work fine though..

[MDK_Marshal]

*stuff*

 

Oh for...

 

Don't cut down your nozzle. That's just asking for trouble, and you'll get gas pissing out of the seal between it and the hop unit, due to the nozzle being too short.

 

I've already sorted this problem out, though nobody seems to have noticed it.

 

Cut down your floating valve.

 

Seriously. Take the nozzle, and try to put a BB on it, as if it was being chambered by the bolt. I'll bet dollars to donuts (or whatever that phrase is) that it won't sit central on the nozzle, and will try and roll off elsewhere.

 

This is because the long thin bit at the front of the floating valve is too long. This will screw up the feeding slightly, due to the BB being all over the place, and, more importantly, it'll push the BB further forward when it' chambered.

 

Snip a few mm off the front of the floating valve, and it'll be shiny. My M4 was having problems with rounds falling out the barrel every now and then; not as bad as yours seems to be, but I still had the problem. The BB's were being pushed too far forwards while being chambered, forcing them past the hop bucking and letting them roll around to their heart's content. Now, with the float valve cut down, it's stopped doing this entirely, and the BB's sit exactly where they're meant to, 100% of the time.

[snorkelman]

aye in default (NPAS) config theres no need for the flute valve to be that long - it's still full length of a PPS valve, yet end of it in an NPAS set up has no need to be anywhere near front of the nozzle.

 

 

[jonny2400]

Guys am looking a replacement drop in bolt set (ie bolt & carrier) , one that fits and works out of the box..... any sugguestions?

 

Also any rumours about a Co2 Mag for the Wa range any time soon?

Edited July 5, 2009 by jonny2400

[raito]

You then need to knock out the roll-pin (#213) at the back of the mag just underneath the cut-out for the mag catch and another pin on the front of the mag (#215).

 

thanks stealth, now i'm stuck on another problem, I can get all the other pins out, but i can't get no 213 out, because it's a hollow type pin... anyone know how to punch out this type of pin?

[LordElpus]

Guys am looking a replacement drop in bolt set (ie bolt & carrier) , one that fits and works out of the box..... any sugguestions?

 

Also any rumours about a Co2 Mag for the Wa range any time soon?

 

considering the gun was designed for 134a i seriously doubt a CO2 conversion is either likely or financially viable.

[stew_b_10]

I finally got into my hop yesterday.

 

The issue i believe is that the nozzle coming forward pushes the bb too far into the hop. the hop rubber isn't shaped to handle this. It may or may not help to shave down the nozzle, but i'll have to wait till i get all of my parts back to see what is possible to do. I don't want to fix this problem but lose the seal. Monday ill be able to take some measurements, do some fitting, and get down to business on this.

 

edit: btw, a small square of electrical tape on top of that spring works wonders. just make sure that there's no grease under it or it will come off of course.

Edited July 5, 2009 by stew_b_10