AGM M4 GBB

[snorkelman]

If you're in that situation Id stick the standard nozzle parts back in while troubleshooting it (your problem was there with those already) saves risking it binding up etc while you have the shiny new bits in and those ending up damaged.

 

Id even consider running it with no bolt catch takes one more variable out of the equation

 

with above two done you can afford to ty and push up on the mag to see if theres an issue with height the mag sits at in relation to the bolt (I wouldnt do that with the new bits in place as you can end up pushing it up high enough to have the mag bind on the nozzle, safer trying it with the stock parts) if putting light pressure on bottom of the mag improves the FPS consistency then I'd look at wether the mag catch is worn letting the mags sit too low, or the seals on the tops of the mags are too thin

 

if there is wobble betweenupper and lower then check the gap between upper and lower isn't too great - to check that you could rest the front lip of the magwell on the lower against a hard surface and push down on the area of the upper directly above there while firing a shot

 

However part of the symptoms you describe doesnt strike me as just a mag sitting too low sounds more like a case of the pressure on valve being too great for the hammer to strike it cleanly - or vice versa force of the hammer being transfered to the valve is too low

 

Hammer Id pull out, clean up the side bushings and refit - making sure the hammer spring legs were seated nice and even on each side of the trigger pin and that theres no grittyness or binding noticeable in the hammer if you slowly work it by hand thru its range of movement.

 

As a side note always have the firing pin block in place when messing around with the hammer - if you dry fire the lower without the firing block in, or even just pull the hammer back to almost cocked and then release it, you can mangle up the wall of the pocket that the firing block sits in due to force of the hammer comming forward under spring tension.

 

 

Are you using those anti rotation pin things that replace the standard hammer and trigger pins, if so are they putting too much pressure on the hammer? is the axis pin they use a little tight and acting as a brake on the hammers forward movement reducing the force it strikes the firing pin with?

 

is the firing pin itself in good condition? not got mangled up at front where its to hit the valve or at rear where its struck by the hammer? If you have calipers measure it up from front to back (a brand new firing pin Ive just measured is 19.42mm from front to back, so yours should be in the 19 to 19.5mm ball park) some folks have a tendency to slam the mags in while the hammer is uncocked and that'll ruin the firing pin.

 

If its undersized then its not going to allow full travel of the valve, and when the mags are full the pressure on the valve is such that nothing less than optimal whack from a hammer resulting in optimal travel of the firing pin wil be enough to get a decent travel in the valve.

 

Whacking mags into an uncocked AGM can also bend the mag valves stem, so that it doesnt end up getting more than a glancing blow from the firing pin whch would result in same thing

 

My AGM is currently being REALLY inconsistent. The power will vary by as much as 70 odd fps, and at the beggining of a mag the gun just refuses to fire; all I get is a little "puff", that'll just about fire the BB, but the bolt carrier won't budge.

 

I take it after each of these pft shots you need to manually rack the bolt in order to chamber the next BB

 

Because of the momentary nature of the hammer strike on the firing pin (no sooner has it struck it than it tends to rebound back off slightly) the amount of travel it can acheive for the valve in that litte instant is kinda critical.

 

If all it acheives is that the valve barely budges, then not only will there be inconsistent FPS there'll also be insuffcient forward travel of the valve to allow the valve lock to pop up into place and lock the valve open.

 

By sounds of it thats whats happening with your pffft shot - cos if the valve stem had entered the mag far enough for the valve lock to kick in and your bolt carrier hadnt budged, then the mag would have vented (cos once the valve lock clicks up into place it needs bolt carrier movement to unlock it again)

 

So only way I can think of that you can get a pffft shot, have the bolt carrier staty where it is and yet not have the mag vent is if the lock hasn't kicked in (or the valve locks on all your mags are broken).

 

By sounds of it eventually after the ten or so shots you've dropped just enough gas pressure in the mag behind the valve to allow the force available to the hammer to be sufficient to trigger the valve a bit deeper - which is when it begins to start tripping the lock and the gun starts to cycle the carrier (albeit with inconsistent FPS)

Edited August 12, 2009 by snorkelman

[ruchik]

That's the problem I'm having, the valve is really hard to push in. But I can't figure out why. The hammer moves smoothly. Just one day, after I reassembled the mag, it started doing that. I've taken it apart and put it back together, no difference. Even sticking the mags in the freezer didn't help.

[MDK_Marshal]

Well, I've gone through most of your list there snorkelman, and it's a fairly comprehensive one!

 

The mags aren't sitting too low, I know that for a fact; in fact, the newer mags are too high, if anything. There's interference with the rubber seal stopping the bolt going all the way forwards perfectly. It seems fine with the spring showing it back, but it I let it go gently without much force, the bolt sticks and gets hung up on the rubber mag seal.

 

I think I've solved the pff issue, mind... the hammer spring was sitting on the bottom of the receiver. I'd taken the gun apart a few times, and , uh, hadn't realised it was meant to sit on the trigger pin!

 

I'm using a bit of drill bit as the hammer pin, actually; the stock AGM pin snapped in half, so I whipped up a replacement. I've polished it up the best I can, and there's no stickyness or grit in the travel of the hammer. I have anti-rotation links en route from RSOV at the moment, amongst other little things, So I'll watch out for those causing problems when they appear.

 

Thing is, I really don't know what's causing the inconsistencies to be so High. I mean, ten fps or so is what I'm expecting... I'm not just setting the bar way too high, am I?

 

 

Thinking about it, though, the nozzle does seem to stick a wee bit in the bolt... *fiddles some more*

[Clastyclay]

Does someone tried to use a useful (custom or quality one) silencer on the gun?

I saw a vid at youtube. But he shot in the bathroom. Some echos and not very expressive.

[ruchik]

Is the floating valve in the nozzle supposed to be sticking out, or recessed into the nozzle? Should it provide tension when pushing against it, or pulling against it?

 

Made another interesting discovery. The mag only stops leaking when I apply pressure to the valve.

Edited August 12, 2009 by ruchik

[MDK_Marshal]

Does someone tried to use a useful (custom or quality one) silencer on the gun?

I saw a vid at youtube. But he shot in the bathroom. Some echos and not very expressive.

 

Not as far as I know, as most of the sound comes from the bolt.

 

Is the floating valve in the nozzle supposed to be sticking out, or recessed into the nozzle? Should it provide tension when pushing against it, or pulling against it?

 

It should be recessed, and should provide tension when being pushed back. The gas pushes it towards the front of the bolt, closing the valve, and forcing the rest of the gas towards the back, powering the recoil mechanism. How far forwards the float valve starts determined how powerful the shot will be.

[ruchik]

So I got myself a GHK mag, no leaks, everything's gravy. Except that it sits too far up, and when fired, just vents all the gas. The bolt clearly cannot overcome the resistance of the mag. Can anyone point out exactly what part of the notch in the mag that catches into the mag release that needs to be shaved?

 

NM it works. Just had to bend the tabs at the top back a little.

Edited August 12, 2009 by ruchik

[Hondatech]

... making sure the hammer spring legs were seated nice and even on each side of the trigger pin...

 

Thanks snorkelman, I was having a wierd low power issue after my hammer pin came apart, and putting the spring legs back up over top of the trigger pin fixed it right up!

[snorkelman]

Thinking about it, though, the nozzle does seem to stick a wee bit in the bolt... *fiddles some more*

 

hop up related issue? BBs not feeding consistently/being gripped fully on each cycle? That'd ruin your consistency in a really random way

 

first thing to check there is that you've got the little rubber buffer in the upper receiver that sits in front of the charging handle, if its missing the charging handle can travel a little further into the upper than it should, which will let bolt carrier (and nozzle) travel further in there too and that in turn will force BB further into the hop chamber than expected.

[snorkelman]

Thanks snorkelman, I was having a wierd low power issue after my hammer pin came apart, and putting the spring legs back up over top of the trigger pin fixed it right up!

 

Good to hear it. Easy mistake to make - those hammer spring legs look like they're made to measure for sitting at the bottom of the lower receiver, whereas on top of the trigger pin is actually the proper place

 

On a related point now you've got them in the right place, take a real close look at the trigger pin and you'll see that one side of it has a groove machined in it, if you get one hammer spring legs to rest right on that groove then it'll help lock the trigger pin in place, and reduce chance of the trigger pin from working its way out of the receiver under recoil.

[Hondatech]

Good to hear it. Easy mistake to make - those hammer spring legs look like they're made to measure for sitting at the bottom of the lower receiver, whereas on top of the trigger pin is actually the proper place

 

On a related point now you've got them in the right place, take a real close look at the trigger pin and you'll see that one side of it has a groove machined in it, if you get one hammer spring legs to rest right on that groove then it'll help lock the trigger pin in place, and reduce chance of the trigger pin from working its way out of the receiver under recoil.

 

After my hammer pin broke in half (They do start life asa single piece, correct?), I've now replaced them with a set of G&P anti rotation pins. They're not too tight on the hammer or trigger, and hopefully won't break or fall out any time soon

 

Thanks again!

[colazel]

if i buy the airsoft surgeon BCG at 77$ at redwolf and i add the ratech NPAS loading nozzle

 

what do you think of thus combo?

[snorkelman]

if i buy the airsoft surgeon BCG at 77$ at redwolf and i add the ratech NPAS loading nozzle

 

what do you think of thus combo?

 

really not sure if the AS standard carrier will be that much better than the stock AGM one? -far as I know its a completely different beast from their lightweight CNC'd ones

 

Other than that really cant say, as with all of these you're biggest issue would be any potential incompatibilities fettling required to get that combo to work together, hopefully someone will have tried them together already and can fill you in on that, otherwise you're kinda acting as the guinea pig

[snorkelman]

 

upper now blasted and first coat of primer

 

 

 

basecoat colour choices

 

decisions decisions will it be 'blue for a boy' or 'pink for a girl' lol Got a few days while the primer job is being completed to make up my mind

[Deepeyes]

Will this fit the agm?

 

http://www.redwolfairsoft.com/redwolf/airs...il?prodID=27470

[colazel]

What the advantage of the winter recoil spring??

[snorkelman]

Will this fit the agm?

 

http://www.redwolfairsoft.com/redwolf/airs...il?prodID=27470

 

Should do As far as I know the inokatsu bolt carrier is longer at the back so RAT supply a seperate Ino/prime carrier, but the npas set itself that they supply is same for all bolt carrier groups.

 

I guess you could email RA-T themselves and confirm wether all the NPAS bolts and nozzles they sell are actually the same.

 

edit - to be honest RA-T really need someone to sit down and rewrite their item descrpitions and explain the differences (if any) between half the options they've got listed on their website. It would clear up a hell of a lot of potential confusion and let folks buy with a little more confidence.

 

 

One thing I would question s wether its worth buying the aluminium npas along with the plastic RA-T nozzle for 80 bucks or just buying the Aluminium NPAS on its own for 60 and fitting that into standard AGM nozzles.

 

Reason for that is the NPAS fits in the AGM nozzle tube just fine, and the chunky plastic AGM nozzle tube is a good fit in the AGM bolt carrier (sideplate is very good fit)

 

in contrast the plastic RA-T nozzle tube has that sort of hard brittle plastic feel about it (dont see it lasting any longer than an AGM one) and from memory I dont think its side plate is quite as good a fit in the AGM bolt carrier.

 

For the 20 bucks extra to have it included you could snag two spare AGM nozzle tubes and have four bucks left over

Edited August 14, 2009 by snorkelman

[snorkelman]

What the advantage of the winter recoil spring??

 

none if you have an AGM spring - both the RAT winter and the stock AGM spring are as near as dammit the same strength (about 3 percent or so difference between them)

 

The RAT summer spring on other hand is around 160 percent strength of the stock AGM and RA-T winter springs

 

[sacairsoftsn00py]

ra-tech winter recoil spring has slightly less tension than the stock agm one....almost un-noticeable...

 

i am running one to preserve my charging handle...even if i am using pc duster to power my agm m4 gbbr

[sacairsoftsn00py]

heres something interesting....one pin reinforcement for the loading nozzle...

 

http://www.filairsoft.com/forum/showthread...378&page=30

Edited August 14, 2009 by sacairsoftsn00py

[snorkelman]

aye if you've bought one may as well get use out of it, personally Ive no plan to buy another one for any other build (based on the wire guage, cpi and ID/ODs a spring strength calc will return results that show only 3 to 5 percent difference between the two)

 

thru pin mod looks worthwhile (means the point where the parts are joined is no longer same point getting whacked by the side lock plate) and shimming gap between bolt face and nozzle tube is always worth while.

 

My only concern would be the extra fidlyness it might need to rebuild a bolt with that mod done to it

 

eg when doing the mod on an assembled bolt its easy enough to use the new longer pin to drive out the original (so the loop on end of the return spring that the original pin holds is never actually free to retract)

 

but if you go back later and push that new long pin out to dismantle part 1 and part 2, then you're also removing the pin that holds the loop on the end of the return spring in place each time you dismanlt the bolt - as the new longer pin is doing both jobs.

 

As a result when you go to rebuild it you cant reach inside the end of part 2 with a pcb hook etc to grab the spring loop in order to fit the short pin thru it (as you normaly could when the pin is a short one). Instead part 2 has now to already be insde part 1 by the stage you're putting the long pin thru, and you've no access to the end of part 2 if its already sat inside part 1

 

Only real way round that I can see is that every time you strip the bolt assembly down you need fit the short pin into the end of the spring loop when reassembling to hold it in place while you still have access to front of part two, then fit the bolt inside the nozzle tube as usual and then finally drive the short pin out with the long one - so the two parts are pinned together and the spring loop is still trapped by the new longer pin.

Edited August 14, 2009 by snorkelman

[sacairsoftsn00py]

Perhaps theres another way to do it. like putting a pin through part number 2 farther up? Ideally though, the closer it is to the base, the better...

 

The Airsoft Surgeon Loading Nozzle seems like its pretty darn sturdy enough to withstand pounding from use of 134a/duster.

 

With the gun shooting over 460 FPS with propane, I don't see why more people are not using 134a or duster gas...

 

duster gas gets you enough FPS (over 300, under 400 with .20g BBs). Your parts will have less wear and tear....which means you will not constantly have to fiddle around with all the parts...

 

besides, propane/green gas aren't really very healthy for AGM/WA magazines. The other mags are okay with them....still, no NLS like the WA magazines...

Edited August 14, 2009 by sacairsoftsn00py

[snorkelman]

GHK mags use multi chambered tubes so in practical terms not too much of a differenece versus using NLS'd WA mags

 

as far as the pin replacement mods goes its probably still worth doing (and only real place to put the pin if you do want to relocate it). Folks just need to be aware that any future rebuilding of the bolt they do might require an extra step or two (and which is probably why we wont see any of the factories adopting that placement of the pin)

 

as far as propane versus 134a goes is hard to tell each individuals reasons, my guess is that it'll be a combo of the following two or three:

 

some folks will want to use propane cos it works out cheaper in terms of gas purchase costs or is easier to obtain/get shipped thru the post

 

others cos its what they use on their other guns and they'd rather standardise on one gas for all (much same reason as Im looking for a CO2 caplet mag to get released at some stage as I run with those on everything else Ive got that isnt externally powered)

 

Then theres the folks who use propane cos 134a blows goats as the ambient temp decreases. Propane suffers from that too, but at say 5 deg C propane is at a pressure roughly comparable to what 134a provides at the normal 20 deg C

 

..whereas at 5 deg C 134a hasnt got the oomph to peel the skin back on a banana much less cycle a GBB bolt carrier

 

but aye if folks are in a decent temp environment, loooking for 300 odd FPS and happy enough with cost of 134a then no real reason not to. What they add in costs of propellant will probably be mitigated by ability not to have to go out and buy big honking spendy bolt carrier groups and regularly replace worn parts, that they would be doing in order to hit 300 odd FPS using propane

Edited August 14, 2009 by snorkelman

[sacairsoftsn00py]

GHK mags use multi chambered tubes so in practical terms not too much of a differenece versus using NLS'd WA mags

 

as far as the pin replacement mods goes its probably still worth doing (and only real place to put the pin if you do want to relocate it). Folks just need to be aware that any future rebuilding of the bolt they do might require an extra step or two (and which is probably why we wont see any of the factories adopting that placement of the pin)

 

as far as propane versus 134a goes is hard to tell each individuals reasons, my guess is that it'll be a combo of the following two or three:

 

some folks will want to use propane cos it works out cheaper in terms of gas purchase costs or is easier to obtain/get shipped thru the post

 

others cos its what they use on their other guns and they'd rather standardise on one gas for all (much same reason as Im looking for a CO2 caplet mag to get released at some stage as I run with those on everything else Ive got that isnt externally powered)

 

Then theres the folks who use propane cos 134a blows goats as the ambient temp decreases. Propane suffers from that too, but at say 5 deg C propane is at a pressure roughly comparable to what 134a provides at the normal 20 deg C

 

..whereas at 5 deg C 134a hasnt got the oomph to peel the skin back on a banana much less cycle a GBB bolt carrier

 

but aye if folks are in a decent temp environment, loooking for 300 odd FPS and happy enough with cost of 134a then no real reason not to. What they add in costs of propellant will probably be mitigated by ability not to have to go out and buy big honking spendy bolt carrier groups and regularly replace worn parts, that they would be doing in order to hit 300 odd FPS using propane

 

 

WA magazines are still the most stable magazine around...even on videos, you can see....it spurts the least amount of liquid propellant...thats why i love em

 

here in virginia, its fairly warm at 85 degrees during summer time. duster works great. probably even better in california where it hits 90-100 degrees...

 

i have thought about getting the npas part....decided against it...

 

why?

 

 

less power behind the bb, more power behind the kick....if using plastic nozzle...not good

 

so, stick with the current loading nozzle...use duster...

 

[Deepeyes]

I just had a chat with Erica from RA-Tech, those parts on redwolf will fit the agm.

 

On a side note. RA-Tech has the most awesome customer service ever.