AGM M4 GBB

[Luis21]

Does anybody know how the RA TECH NPAS BCG copes on 134a gas and what fps can be achieved using 134a and an NPAS BCG? I ask since 134a is readily available to me...

 

FPS should be good, about 400 FPS however the bolt carrier will cycle rather sluggishly.

 

The stock BCG is said to be 209g and the NPAS BCG is said to be around 241g. The extra weight will make it harder for the 134a gas to cycle the BCG in a fast, snappy matter. Not to mention the extreme cooldown using 134a compared to green/propane.

 

I've never tried an NPAS BCG w/ 134a but I've tried everything else...

 

@MDK Marshal:

 

Sounds great! Thanks for the heads up. I'll be getting 6 5KU mags which are the same design as the version 2 AGM mags so hopefully they perform just as good.

 

-Luis

Edited July 28, 2009 by Luis21

[Roecar]

Out of curiosity, how does one swap nozzles on the NPAS? At the moment I have plastic ones but in the future I may want to use aluminum ones when I feel more comfortable with internal work.

[snorkelman]

they screw in/out

[Luis21]

they screw in/out

 

Thanks. And the NPAS BCG comes with 1 plastic nozzle correct?

 

-Luis

[snorkelman]

yep the one thats fitted in it when you buy it is plastic one

[Luis21]

yep the one thats fitted in it when you buy it is plastic one

 

Thanks again Snorkel.

 

I need $$$$........

 

-Luis

[sacairsoftsn00py]

I super glued the O-ring that seals against the brass ring (with a bigger o-ring)-the one which gets opened when the pin is hit by the firing pin. On 3 of the 1st Gen. AGM M4 GBB magazines that I have done that to, none of them leak. I have fired one full magazine on each of them doing semi-auto and 2-3 round bursts today. It was about 80-85 degrees out today though room temp where I loaded the magazines was 70 degrees.

---------------------

 

Here are some photos of my gun:

 

 

The hop unit moves freely back and forth about 3mm. I inserted a spring that pushes the hop back to eliminate free movement. This in turn gets me the same hop unit-nozzle seal every time i shoot the gun.

 

 

Guarder Soft/Clear Type Hop Bucking protruding down the chamber of the hop unit.

 

 

G&P Sear and Bolt Stop. Both straight Drop In Replacement/ Upgrade parts.

 

 

Plain Jane M4 RIS. G&P Anti-Rotation Links and Airsoft Surgeon Light Weight Bolt Carrier shown.

 

-------------------------------------

 

Edit:

 

Looks like I will be getting my WA M4 Magazines on July 31st. Thanks AEX!

Edited July 29, 2009 by sacairsoftsn00py

[Luis21]

Looks good Snoop.

 

But man that Pro-Arms hop-up chamber has way too much space to move around. The adjuster on the stock chamber fills up the hop-up hole in the outer barrel quite nicely. I tried pushing mine with both my finger and with the loading nozzle forward and back to check for movement and there was ZERO play with the stock hop-up chamber.

 

Have you fixed your RIS wobble yet?

 

-Luis

[Stealthbomber]

Just thought I might give you lads all a heads up...

 

Remember when I said that my Gen 2 AGM mags were holding gas from a skirmish a few days before?

 

Well, A good couple of weeks have passed, and they're still holding the same gas with no problems or leaks. At all.

 

So, if you're after dirt cheap mags, the newer AGM ones will work perfectly fine, it seems. As far as holding gas goes, at any rate.

Do they work the bolt catch though?

[sacairsoftsn00py]

Looks good Snoop.

 

But man that Pro-Arms hop-up chamber has way too much space to move around. The adjuster on the stock chamber fills up the hop-up hole in the outer barrel quite nicely. I tried pushing mine with both my finger and with the loading nozzle forward and back to check for movement and there was ZERO play with the stock hop-up chamber.

 

Have you fixed your RIS wobble yet?

 

-Luis

 

The Pro Arms Hop Up Unit only moves about 1.5mm (at most) now because of the spring I installed. When compressed, the hop unit only moves forward by 1.5mm (at most).

 

Lock the bolt carrier back, take off the bottom part of your handguard/RIS and push the hop unit back, then push forward on the stock hop through the ejection port....put your finger on the feed tube part of the stock hop unit and see how much play there is...

 

I broke one of the tabs on the delta ring. Bonjour drilled some material off of his RIS...I did the opposite before his post. I figured that the delta ring is actually the same one that AGM uses in their AEG line and that the purpose of the tabs was the same as that of a Tokyo Marui's delta ring...its to keep the delta ring from spinning, and accidentally being disassembled where the delta ring comes out along with the spring.

 

I have zero wobble on my RIS. I eliminated the front to back movement by sticking an O-ring to push back on the handguard's front retainer cap. I just have to fix the upper receiver to lower receiver wobble. Looking at the hole where the rear receiver pin is, that area has too much space. I am thinking about cutting down aluminum possibly from a soda can and inserting/gluing it into the hole to minimize play. If I decide to do that, I will post up my findings....maybe a picture

 

[Luis21]

Sounds good Snoop.'

 

I actually did check my hop-up unit by opening up the RIS and pushing it back towards the bolt carrier. I pushed it every single way possible and there is no movement.

 

The Pro-Arms chamber, without the spring, is just too short for the AGM outer barrel hop-up hole. However since it takes AEG barrels and buckings I'd buy it still and do the spring mod.

 

I also drilled my RIS just like Bonjour43 and it's solid now. However when drilling the front sight I ended up making a hole through the thing! The metal on this gun is way too soft! Too cheap, I was surprised.

 

Not only is it cheap but it's also heavier than good aluminum. The lead and other pot metals make it heavy.

 

My G&P RIS, which is the same as the real Knights Armament, has more components than the AGM RIS. Yet it's lighter and way stronger. Same with the delta ring materials. The AGM pot metal isn't good at all, thank goodness it doesn't take the same stress as a real gun.....

 

And yes, AGM used the same delta ring that they use in their AEGs, that's why it's so weak and the hole for the gas tube is way different from the real M4.

 

Buying a G&P sounds good right now......

 

Their externals are great!

 

Heck I'm thinking about buying an Inokatsu, have you seen those!?

 

But I'm satisfied with my purchase 100% because I put my work into it and brought it up to my standards. Standards which I trust and know won't fail me out on Saturdays while playing soldier.

 

The AGM has alot of potential and is as good as YOU make it by putting in work. You have to make it good.

 

Things are only going to get better since I'm going to get the NPAS BCG soon....

 

-Luis

 

[sacairsoftsn00py]

Hm. I have not really put the stock hop up against the Pro-Arms one so I don't know what the difference between the two is length wise. Clearly, with my setup...the bolt face comes in contact with the hop unt. The spring pushing the hop unit back not only creates a more consistent chamber-nozzle seal, but also also acts as a buffer. Since the bolt face hits my hop first, the gas key of the buffer does not hit the metal block that it catches on when you pull the charging handle back. That just means it is less likely to break.

 

My goal was to make the gun reliable. I did not want it to kick the hardest. Having hard kick just means added stress to parts that were not meant to withstand such distress.

 

My bolt carrier group setup and hop unit seems to be holding up well after about 3000+ rounds through it. My bolt carrier has probably seen about 1500 rounds through it along with the Pro-Arms Hi-Power Loading Nozzle.

 

BTW, the spring that I used to push back on the hop unit was off of a G26 spring guide. The spring has enough tension to keep the bolt carrier from going all the way forward to where it should be when the bolt carrier is slowly let go (The fact that I am using a lighter tension recoil spring doesnt help) I just use the forward assist button to push the bolt carrier group.

 

When shooting the gun, the bolt carrier group moves all the way forward as it should.

 

 

Still, with the combination of parts that I have used, I have had zero breakage of the upgrade parts. The only thing I have really broken is the stock sear (which kept me from shooting semi auto). Other parts have held up....

 

I have had zero problems of the parts I have not being able to get my gun shooting aside from the incompatibility between AS loading nozzle part #2 and my Pro Arms Loading Nozzle body. Still, the AGM part #2 is still holding its own.

 

While I have thought about how nice it would be to have an adjustable FPS/blow back....I have heard so many issues with the RA-Tech NPAS BCG. Other than cross compatibility of parts between brands, the setup I am running has proved to work flawlessly for me.

Edited July 29, 2009 by sacairsoftsn00py

[sacairsoftsn00py]

 

On another forum, someone pointed out that the full auto sear spring (left silver spring on the left side of the photo) is not on properly. The right position of the spring can be located on the diagram on this photo:

 

 

Upon inspection of the setup and the parts, I found that correct spring placement also keeps the selector lever from popping out of the lower receiver when the lever is pointed to safe. The spring blocks the trigger from sliding out of the receiver when it is on safety.

 

Try it out. Put the selector lever on safe and push the other end of the selector lever in. You will find that the selector lever will pop out. Do not pop the selector lever all the way out as it might prove to be tricky installing the selector back in place.

 

 

[RUSHER2]

I super glued the O-ring that seals against the brass ring (with a bigger o-ring)-the one which gets opened when the pin is hit by the firing pin. On 3 of the 1st Gen. AGM M4 GBB magazines that I have done that to, none of them leak. I have fired one full magazine on each of them doing semi-auto and 2-3 round bursts today. It was about 80-85 degrees out today though room temp where I loaded the magazines was 70 degrees.

---------------------

 

Here are some photos of my gun:

 

 

 

The hop unit moves freely back and forth about 3mm. I inserted a spring that pushes the hop back to eliminate free movement. This in turn gets me the same hop unit-nozzle seal every time i shoot the gun.

 

 

 

Guarder Soft/Clear Type Hop Bucking protruding down the chamber of the hop unit.

 

 

 

G&P Sear and Bolt Stop. Both straight Drop In Replacement/ Upgrade parts.

 

 

 

Plain Jane M4 RIS. G&P Anti-Rotation Links and Airsoft Surgeon Light Weight Bolt Carrier shown.

 

-------------------------------------

 

Edit:

 

Looks like I will be getting my WA M4 Magazines on July 31st. Thanks AEX!

 

 

 

 

I hope you dont store your AGM in safe! it wears down the springs ! maybe you racked it and put it into safe idk?

 

should always be stored in single!

Edited July 29, 2009 by RUSHER2

[sacairsoftsn00py]

I store my gun in semi. I take pictures messages my gun in safe. It is on safe because i cocked my gun to insert the magazine and 4 do not want any accidental discharge when handling it. If you must know, i keep my magazines charged with gas but not inserted into the gun. Do you have any constructive criticism to share that would contribute to the thread?

[Luis21]

@Snoopy:

 

Yeah, that's real nice that you found a reliable way of running your AGM. We thank you and many will find it very useful.

 

Again I must say that even though it's an easy fix, the spring on the hop-up chamber is a very clever idea.

 

-Luis

[stew_b_10]

luis, if you think about it, a lot of AEG chambers also have spring tension. it is like that for a reason

 

and snoopy, i think that he did contribute to the thread by warning to those who store their gun on safe like an AEG. I think you took it personally and i don't think its intent was malicious.

[RUSHER2]

luis, if you think about it, a lot of AEG chambers also have spring tension. it is like that for a reason

 

and snoopy, i think that he did contribute to the thread by warning to those who store their gun on safe like an AEG. I think you took it personally and i don't think its intent was malicious.

 

 

+1 Took it the wrong way.

 

I contributed. by telling the new Gun owners of the GBB's after having AEG's and havent handled a real AR' That when you store in safe its bad for the gun.

 

Just trying to help.

 

 

 

GBB FTW!

[stew_b_10]

That being said, i think that you overplayed it and kind of came off as a know it all, especially with the exclamation points and stuff. kind of overdramatic. and you definitely arent helping your case with the rolling eyes smiley. unecessary.

 

lets all be friends and get back on topic.

 

 

ill be posting pics of my finished gun after i finally get my order from EBB. if ever.

[Roecar]

An interesting development with my internal setup, I've completely shattered my first plastic nozzle on my NPAS. Looking into what might have caused it, I think the G&P hopup rubber is to "thick" where I physically cannot push the BBs out unless I apply a fair amount of pressure. That said when the gun does cycle properly I'm probably getting an insane amount of FPS since a lot of force is necessary to push BBs out.

 

Has anyone else experienced this before? I'll be asking my local GBBR tech at Evike what might be causing this. For now I'll be shelving my gun since I don't want to trash $315 worth of parts...

[Bonjour43ma]

Bonjour-

 

Have you tried fiddling around with the stock hop unit? Could you try something out for me? Could you remove the lower RIS, lock the bolt carier back using the bolt catch, then push back on the hop dial (towards the buffer tube), then push the hop unit forward (towards the barrel). Could you let me know how much (front to back) play you get with the stock hop unit/inner barrel assembly?

 

hey - I did what you had described and there is no movement. The hop unit doesn't move at all either from the hop dial (pushing back) or towards the barrel (pushing forward). Is it supposed to move a little? The hop rubber seems to function properly as I can see it raise up and down as I turn the dial. BBs don't roll out of the barrel either when I point the gun downwards.

 

 

I also noticed a few things:

 

- there is a hole on the stock hop-up bucking. Do I need to seal it to improve gas efficiency?

- the rail on the top receiver dones't line up with the top rail on the RIS. The RIS is just a bit higher. Also, if I removed the carry handle and look down towards the front of the gun from where the charging handle is, I can see that my front sight is slightly off to the left, along with the RIS, and both do not lineup straight with the top receiver. They are off by just a little bit and you can't see it unless you do what I did. Will this affect accuracy? I surely hope that my barrel isn't bent

- I noticed very very slight movement between the top and lower receivers. very slight, almost not noticeable unless you know where to push.

 

 

The diagram you had posted about the selector spring is very interesting and I did try putting the gun in SAFE, and pushing the pin out - and it DID try to come out! Whoa! Have you flipped the selector spring around to its proper position? Does it make a difference?

 

I am slowly starting to understand why this gun is 1/4 the cost of a WA... there is almost no QC/QA at all on them and the manufacturing fault tolerance is VERY high. lol

 

This is definitely a gun you need to spend time on to make it work like it's supposed to, otherwise it will most likely break down after a few hundred rounds.

[Bonjour43ma]

Also... I cannot, for the life of me, knock out the pin at the base of the front sight that holds the sling attachment ring. It just won't come out no matter how hard I hit it with a hammer. Any tips on how to remove it? I don't use a sling and hate the "clank clank" sound that the sling ring makes when you move the gun around.

 

Thanks!

[Roecar]

You have to remove the entire front sight post and the sling attachment will slide off with it.

[Bonjour43ma]

You have to remove the entire front sight post and the sling attachment will slide off with it.

 

ah... so I can't remove it with the front sight still on the barrel? Something to do with the tension from the two other pins above it?

 

Will give it a try... thanks!

[sacairsoftsn00py]

An interesting development with my internal setup, I've completely shattered my first plastic nozzle on my NPAS. Looking into what might have caused it, I think the G&P hopup rubber is to "thick" where I physically cannot push the BBs out unless I apply a fair amount of pressure. That said when the gun does cycle properly I'm probably getting an insane amount of FPS since a lot of force is necessary to push BBs out.

 

Has anyone else experienced this before? I'll be asking my local GBBR tech at Evike what might be causing this. For now I'll be shelving my gun since I don't want to trash $315 worth of parts...

 

This is one of the reasons why I opted not to get he complete NAPS kit from RA-Tech. I have read through peoples experiences with it and your experience is pretty much text book.

 

What kind of recoil spring are you running? The bolt carrier group slams forward with a decent amount of force...enough force that would push the BB through the hop bucking to chamber a round.

 

Also, unlike AEG's Green Gas/134a gas and pretty much the other propellants expand over time. A slight delay through the bucking because of a good seal could be a good thing. It is when the BB's jam that the gun becomes useless

 

Check out "gas guns info". There's over 3500 posts on there but you'll come across documentation of what happened in your case.

 

 

hey - I did what you had described and there is no movement. The hop unit doesn't move at all either from the hop dial (pushing back) or towards the barrel (pushing forward). Is it supposed to move a little? The hop rubber seems to function properly as I can see it raise up and down as I turn the dial. BBs don't roll out of the barrel either when I point the gun downwards.

 

 

I also noticed a few things:

 

- there is a hole on the stock hop-up bucking. Do I need to seal it to improve gas efficiency?

- the rail on the top receiver dones't line up with the top rail on the RIS. The RIS is just a bit higher. Also, if I removed the carry handle and look down towards the front of the gun from where the charging handle is, I can see that my front sight is slightly off to the left, along with the RIS, and both do not lineup straight with the top receiver. They are off by just a little bit and you can't see it unless you do what I did. Will this affect accuracy? I surely hope that my barrel isn't bent

- I noticed very very slight movement between the top and lower receivers. very slight, almost not noticeable unless you know where to push.

 

 

The diagram you had posted about the selector spring is very interesting and I did try putting the gun in SAFE, and pushing the pin out - and it DID try to come out! Whoa! Have you flipped the selector spring around to its proper position? Does it make a difference?

 

I am slowly starting to understand why this gun is 1/4 the cost of a WA... there is almost no QC/QA at all on them and the manufacturing fault tolerance is VERY high. lol

 

This is definitely a gun you need to spend time on to make it work like it's supposed to, otherwise it will most likely break down after a few hundred rounds.

 

 

It is when you actually put BBs through your gun that you might experience the BBs rolling out of the barrel. With green gas, the bolt carrier group blows back so forcefully that the BBs end up getting chambered too far into the hop unit. Another thing that does not help is the fact that the flute valve also pushes the BB an extra mm. I would suggest trimming it if all else fails (new hop bucking/new hop unit). You might experience it when you shoot BBs through your gun using green gas. Until then, you most likely will not experience it.

 

I have noticed the very same things about the gun. They just have not really bothered me as much as I know that eventually, I will get a front sight that clamps on to the outer barrel instead. Probably just a gas block, or a flip up sight. Yes, the RIS sticks about 2mm more than the upper receiver's rail. There's no real way to modify it so the two line up.

 

The font sight is as is unless you decide to shave down some metal. Personally, It does not affect accuracy. Pesonal preference I suppose.

 

I too have a hole in my stock hop bucking. That issue has also been documented in other forums.

One fix for it would be adding material using rubber cement. Personally, I would rather just get a G&P hop bucking for it.

 

I thought I posted that I stuck the full auto sear spring into the correct orientation earlier. Hmm...Wellp, I did The spring keeps the selector lever in place. Granted that you can still push the lever in about 1/5" but it will not come out unless you really force it out. On semi and full, you do not have to worry about the selector coming out.

 

Also... I cannot, for the life of me, knock out the pin at the base of the front sight that holds the sling attachment ring. It just won't come out no matter how hard I hit it with a hammer. Any tips on how to remove it? I don't use a sling and hate the "clank clank" sound that the sling ring makes when you move the gun around.

 

Thanks!

 

I just used a "punch" and tapped it with a hammer