AGM M4 GBB

[mutikasha]

Try to see if your side lock plate is busted. If indeed it is there is nothing to initially pull the nozle back into the BC no mater the spring strength. If you are using alu nozzle this indeed could be your problem.

[yetifas]

Have my AGM running ok so far, but for experiment I removed the flute valve. When I tried firing it, the gun cycles! Chrono readings goes up dramatically. Only thing is gas on mag is depleted real quick.

[JM360]

Have my AGM running ok so far, but for experiment I removed the flute valve. When I tried firing it, the gun cycles! Chrono readings goes up dramatically. Only thing is gas on mag is depleted real quick.

 

Gas gets depleted real quick? I don't quite see the connection of the amount of gas released with the removal of the flute valve. Gas released from the mag is mainly due to how hard the hammer punches the gas and how long the valve was opened during that time.

[Luis21]

Do you get intense blowback?

 

I guess that the BCG dwells a bit longer since the flute valve isn't there to direct the gas, thus resulting in more gas consumption....

 

-Luis

[oikoik]

um.. ordered one of these..

anything to watch for? just stock, not real interested in accuracy yet... just want some gbb fun

and is unco still best place for mags?

[mrpugster]

nice M4 Polecat :-)

[yetifas]

Gas gets depleted real quick? I don't quite see the connection of the amount of gas released with the removal of the flute valve. Gas released from the mag is mainly due to how hard the hammer punches the gas and how long the valve was opened during that time.

 

 

My guess is that with the flute valve the gas expelled from the magazine is quickly diverted towads the rear blowback function, even if the hammer is still in its cocking stage. By the time hammer is fully cocked, the flute valve is fully closed for some time and BB is propelled out of the barrel.

Flute valve acts as an efficiency part of the whole system, shooting the gun without it I noticed that there are excess gas blown out of the barrel, way too much am sure.

 

The secret to having high chrono readings with the flute valve is to make a harder flute valve spring. This retards the flute valve to closing fast and gives more gas time to the barrel.

Its a yin and yang thing, barrel gas - blowback gas.

 

As for blowback I do not get as much as with the flute installed, but still somekick to it. Another trick to efficiency is to seal part no. 4, very important!

[3vi1-D4n]

Increasing flute valve spring tension may have issues if temperature drops under 14*C, and slows the impulse of the blowback. You are lucky that most of you are in warm temperate countries most of the year.

 

 

Where I am, temperatures can range from 30*C to 16*C for summer and 18*C to 2*C in winter.

 

Here is the issues I have observed when using the AGM:

 

- I was fixing an AGM which would not fire when temperatures got hotter than 27*C. The hammer would drop but no gas/very little gas was coming out. As soon as it cooled down, then it would fire.

 

- At 14*C, I had to change the flute valve spring from the stronger RA tech NPAS spring to the default weaker AGM one because the FPS was low and blowback was weak/inconsistent in strength. The blowback was sluggish.

 

Even with the WE M4, I have had to cut 1.5 rungs of springs from the flute valve because it would just vent gas when the mags/gun got cold on its stock flute valve spring, while standard pistols still functioned.

Edited June 29, 2010 by 3vi1-D4n

[yetifas]

Youre absolutely correct sir, not to mention cooldown is faster on colder countries. I think if I live in a cold place I would opt for aegs, even with

batteries not agreeing with the weather you can still compensate for higher amperage or voltage.

[JM360]

My guess is that with the flute valve the gas expelled from the magazine is quickly diverted towads the rear blowback function, even if the hammer is still in its cocking stage. By the time hammer is fully cocked, the flute valve is fully closed for some time and BB is propelled out of the barrel.

Flute valve acts as an efficiency part of the whole system, shooting the gun without it I noticed that there are excess gas blown out of the barrel, way too much am sure.

 

The secret to having high chrono readings with the flute valve is to make a harder flute valve spring. This retards the flute valve to closing fast and gives more gas time to the barrel.

Its a yin and yang thing, barrel gas - blowback gas.

 

As for blowback I do not get as much as with the flute installed, but still somekick to it. Another trick to efficiency is to seal part no. 4, very important!

 

Exactly the point. The flute valve only dictates the division of gas for bb propulsion and bolt blowback. But that does not affect gas consumption since the amount of gas released by the mag is always the same. You can have a strong fps output and weak blowback, or weak fps and strong blowback, stil the amount of gas used will be the same. As soon as the hammer strikes, it lifts up immediately (if it doesnt then your mag will purge as soon as the bolt goes back.

[yetifas]

Hmmm, I now see your point sir, ALL gases expelled from mag is either diverted to blowback or bb propelling duty. So its either having higher chrono readings or higher blowback. But am sure you will agree with me that efficiency on gas expelled is crucial in any case, as gas should be used exclusively on those two actions only. As I mentioned earlier part no. 4 has a lot of leak. What I do is use a small o-ring, the one installed on nozzles on aegs and straddle this on part no. 4, this will seal the rear blowback chamber beautifully. Also lubricate using grease on the insides of BCG so large o-ring is sealed as well.

So many things to consider on our GBBRs, recoil spring/ hammer spring stiffness, porting of mag valves, just to name a few.

 

Personally would rather work on the stock parts before seriously buying upgrade parts though.

 

 

 

My AGM GBBR. Always install a magpul on the magazine, this will act as a cushion on the magazine in the event of dropping this accidentally, and lessen damage/ cracks that may lead to an explosion. Its also easy to pull the mag from the chest rig as well.

Edited July 5, 2010 by yetifas

[Megalomaniac]

The evil GBB monster started looking at me again, is there a definitive list of what upgrade parts are needed to make a stock AGM into a reliable skirmish gun?

[D-JHapyMeal]

Well, you could try to buy the RA-TECH AGM M4. They fixed quite some things to make it skirmishable.

[3vi1-D4n]

I would like to know, how many people have seen broken aluminium bolts on their WA/AGM/G&P/Inokatsus? And which operating temperatures were they from?

[TheFull9]

I'm thinking this kit might be a good replacement to straight-out overhaul the internals in the lower:

 

http://shop.ehobbyasia.com/upgrade-part/parts-upgrade-pistol/valves-kits/gandp-wa-reinforced-assemble-parts-frame-set-for-wa-m4-gbb.html

 

Alu rather than steel, but hopefully it would avoid any fitting issues being all the same manufacturer. Any thoughts?

[mutikasha]

I seriously doubt in these parts all being alluminum. I have several internal GP parts and they are made of something steel like, definitely not alu. Some parts may indeed be made from alu (buffer, firing block, etc.).

[TheFull9]

Well I'm just going off the product description to be honest, I wouldn't have thought G&P would advertise it as being all aluminium alloy if it wasn't, though stranger things do happen in airsoft it has to be said.

[UrPeaceKeeper]

This seems like the logical place to ask a question like this (with the high probability of running into someone who has used this part), but has anyone used the Big Dragon High Flow Valves for their magazines yet? I'm looking to replace some Bomber Main Valves in two of my mags (one with a chronic leak) and if they are worth a hoot to replace all of the valves in my magazines with the same. Replacing with the same, and supposedly highly available valves would be nice for consistency's sake, but I dont want to take the leap of faith and buy 7 of these just to get bit and have worse performance than the stock WA valves in 3 of my magazines in the 2 bombers in my other two mags and the 2 stock valves in the 2 KA mags I plan on buying as well. Especially with a steel bolt carrier that I can barely get 30 shots out of anyway (Element bolt carrier will go under the milling machine to lighten up alot more!) Part of that may be the damaged blow back O-ring, but the main valves being a bit restrictive are not helping either in the 2 with bomber valves, which barely cycle for 15 rounds on propane before venting =(.

[Warpix]

Hey guys, finally got around to playing around with my AGM again and found that it seems that the threading where the barrel nut attaches is stripped. I got a new delta coming in hoping that it may fix my problem, but still. Does anyone know a cheap fix for this? All I really found was that I could get the AABB metal body from EBairsoft for about $60, but seems like a waste when I only need the upper receiver. Past that I'm thinking maybe a re-threading tool.

[TANGO91]

Does anyone know what type of threading the clone UBR stock tubes have, G&P or WA?

[nickthebrick65]

Hey guys, finally got around to playing around with my AGM again and found that it seems that the threading where the barrel nut attaches is stripped. I got a new delta coming in hoping that it may fix my problem, but still. Does anyone know a cheap fix for this? All I really found was that I could get the AABB metal body from EBairsoft for about $60, but seems like a waste when I only need the upper receiver. Past that I'm thinking maybe a re-threading tool.

 

I was going to say you could use a free float rail system, but then realized your upper is messed up, not the delta ring, sorry.

Edited July 28, 2010 by nickthebrick65

[Warpix]

Turns out that it was my barrel nut. I replaced the stock one with a real steel barrel nut and it holds it nicely, but due to the dimensions of the new barrel nut, my delta sits a little more forward than normal. But I was able to run three mags through it without the barrel wobbling at all. My friend says he had the same problem, so he's got a full real steel delta assembly sitting on his AGM, but his sits where the AGM delta used to. For me this unfortunately means that I'd have to sand any hand guards down a little bit before they fit, but hey, I was planning on picking up a magpul hand guard up anyways.

 

@UrPeaceKeeper

 

Sorry man, can't help you there, but tell us how that works out if you do that. One of my GHK mags just decided to blow out all its gas.

[yetifas]

Been toying around for a few months on and off regarding putting a small piston inside the nozzle. My point being that recoil gases used is too much for the WA system. Adding a piston inside the nozzle to push the BCG back would dramatically reduce the gas consumed on blowback.

Finally was able to do this with success, highest reading so far on .2 is 450 fps, can probably up the readings by using a stronger flute valve spring. I can also finish 30 rounds easily on one trigger pull! After 30 rounds there is still enough gas inside for another load of BBs.

Cool down is not as bad as stock setup since I do not need a lot of gas per shot. The only drawback is BCG does not cycle fully rearwards so no bolt lock function. Also recoil is quite tame comparatively.

 

 

[UrPeaceKeeper]

Been toying around for a few months on and off regarding putting a small piston inside the nozzle. My point being that recoil gases used is too much for the WA system. Adding a piston inside the nozzle to push the BCG back would dramatically reduce the gas consumed on blowback.

Finally was able to do this with success, highest reading so far on .2 is 450 fps, can probably up the readings by using a stronger flute valve spring. I can also finish 30 rounds easily on one trigger pull! After 30 rounds there is still enough gas inside for another load of BBs.

Cool down is not as bad as stock setup since I do not need a lot of gas per shot. The only drawback is BCG does not cycle fully rearwards so no bolt lock function. Also recoil is quite tame comparatively.

 

How does the blow back feel? I also toyed around with steeling the NS2 style gas system and hijacking it for the WA system, but without access to a machine shop to make new bolt carriers and nozzles it was a dead end adventure. I still have the ideas rolling around in the head of mine, but I'm not sure how much it truly matters

 

I'm curious to see how you did it?

 

As for the Big Dragon (READ: ENERGY) High flow Valves, give them a miss.. the shafts on them are too long to cycle correctly with a 150% hammer spring in my WOC and WA mags, and the ones I cut down with the mill either runaway firing or double tap every time. Stock WA valves are fine, just need to find a source for good quality valves... How do the AGM valves compare to WA valves (Read: How does an AGM mag compare to the WA Mags in terms of felt blow back and FPS?)

[yetifas]

Blowback feels like a gbb pistol on green gas, definitely not as strong kicking as before my mods.

Will try to post a photo on that custom piston I intalled.