Fps Issue - Gg M4

[Gareth2021]

Hi all, 

I’m currently having an issue with FPS. I tested my M4 and it was kicking out 306FPS using 0.2 @ 0.84 Joules. (Stock)

My aim is to get 295FPS using 0.28 as from what I understand that is the equivalent to using 0.2 and getting 350FPS. 
 

So I bought a Laylax Non-Linear AEG Spring MS100. What I was recommended by the Airsoft shop as they explained it would normally provide 330FPS using 0.20, however with it been a long barrel it would give more FPS.

I’ve changed the spring and I’m actually getting 297FPS with 0.20 and 245FPS with 0.28. (Lower than previous spring)

Strange how I’m getting lower FPS with a new spring. 
 

The rifle I own is: G&G AEG TR16 MBR 556WH with G2 ETU

The site I go to has a limit of 350FPS for automatic, so I’d like to be getting as close as I can to the equivalent using 0.28.

I’ve attached an image showing details of test and these figures are with no Hop-up on. 

Any ideas of where I’m going wrong or what I need to do? 
 

Any help appreciated. 
Thanks

View attachment 74689

 

[Rogerborg]

Evening.  Barrel length isn't that important in airsoft.  I've got an MP5K with an M100 spring shooting at 1.04J through a 110mm barrel, and an M4 which hit 1.3J (oops) from M100 and 229mm (I dropped to an M90).

The secret is air seal.  Your G&G looks like it's got decent parts, like a double o-ring nozzle and cylinder head.  But the rubber can dry out and deteriorate, and airsoft quality control is pretty random.

Ideally I'd suggest opening your gearbox, lubing all the o-rings, and stretching the piston o-ring.  That's easy enough to do, you just get it off the piston head, stretch it over the cylinder, and heat it up with a lighter or other heat source.

If you're wary about doing that, the quick bodge is to split the receiver and get some silicone lube (oil or spray) into the nozzle so that it ends up inside the cylinder.  Swish it around, give it some time to work into the o-rings, then give it blast on auto before you put it back together so that it blows the excess out the nozzle rather than into your hop rubber.

The other easy thing to check is your hop rubber, which might have dried out and be giving a bad air seal.  They're cheap enough to replace (Maple Leaf rubbers are great) or you could lube it with silicone oil or spray and see if that perks it up.  It's actually fine to get silicone inside the rubber, just clean it out afterwards. You might get a few wild rounds but it'll soon settle down.

 

[concretesnail]

As you have changed the barrel I'd start by checking the air seal of the hop rubber to the barrel and into the hop unit. If any seals a bleeding air then you'll be dropping the fps. Then ehen you reassemble make sure the barrel and hop unit are pushing back to seat on the nozzle correctly.

 

[ak2m4]

you sir have a compression leak either in the hop chamber / rubber or in the gearbox. 

chamber problems are easier to work on but gearbox issues you'll have to open her up.  have a youtube search on "aeg compression tests".  as roger says could just be something as simple as replacing or lubing orings

 

[Rogerborg]

As you have changed the barrel

Click to shrink...

I don't think that OP has changed the barrel, just that it's 400mm to begin with, and it seems to have a full cylinder.  It looks to have been designed as a DMR platform and with all those o-rings it should be capable of reaching or exceeding site limits - if everything is sealing OK.

 

[Gareth2021]

Thank you everyone that has commented so far, going to test out all the above tomorrow and get some grease bought. 
 

Yes, I haven’t changed the barrel it’s stock, it’s just the guy at the Airsoft shop said with it already having a long barrel it should increase. However that’s good to know Roger about your experience. 
 

I’ll watch the videos on YouTube and will update you all!  
 

Really appreciate everyone’s help, thank you!! Will update immediately once I’ve done all the above ? 

 

[Rogerborg]

Best of luck.  The thing about airsoft is that it's not an exact science, and by that I mean that it tends not to be reproducible. The quality control is all over the place, and it only takes a fraction of a mm gap to reduce air seal.  It could be something as simple as the barrel not being fully seated in the hop, or the hop unit not being pushed back against the gearbox hard enough by whatever spring or o-ring is supposed to be doing that.

It's really a case of trial and error to see what works for your particular gun, and I'd go with the easy stuff first.

 

[Shamal]

  The thing about airsoft is that it's not an exact science, and by that I mean that it tends not to be reproducible. 

Click to shrink...

Well I'm not too sure  about that.

I started of with one gun and it seems to have reproduced  many! ?

Regards 

 

[Gareth2021]

Update!!!
 

took it all apart and got into the gear box, checked the cylinder air pressure with and without the nozzle. Tested with the plastic guard as I understand it pushes it away and everything seemed fine but I heated the O ring just in case and greased up. 
 

Also the hop up rubber looked in good condition but I thought may have possibly been dry and that’s the reason as you guys explained, so cleaned it up and greased it. 
 

Put all together after having some issues putting the receiver back on, the results are below: 

0.20 firing average 325fps @ 0.98 Joules

0.28 firing average 265fps @ 0.91 Joules (did have one that fired at 286fps @ 1.06 joules which would be happy if that was consistent) 

The above results are probably correct with the spring that the shop provided me with as explained at the beginning which is suppose to give around 330 FPS with 0.20. (Even though I’d explained what I was looking to achieve) 
 

I’m thinking for myself to get as close to 295fps with 0.28 I’d have to buy a 110 spring which gives around 360fps with 0.20 and cut the spring if it’s going over? 
 

Or any other recommendations on how I could reach the desired fps? ? 

 

[ak2m4]

Buy a M110 spring, fit it then chrono to work out starting fps. maybe run 1000 bb's / cycles through it, leave compressed in the aeg over night.  then chrono.  at this point you can either try taking a coil off or you can short-stroke 1 tooth.

another option check to see what if the spring guide and piston head have a thrust bearing installed, if one is missing you can perhaps install one with the M100 or remove one of them with a M110, that might make a small difference.

Either way 325 fps is perfectly respectable, sometimes it's better to leave as is

As @Rogerborg says Airsoft isn't an exact science, spring designs differs in how they are rated, add to that all the other variables involved etc. 

 

[Rogerborg]

Great, that's an improvement, and that's what I'd expect from an M100 spring.  100 is notionally 100 metres = 328 feet on 0.2g.  Aside I can't be doing with 0.2g fps numbers, as who's using 0.2g BBs these days?  But we are where we are.

With a long barrel and heavier BBs you want a bit more puff behind them, so if you're happy that it's as good as it's going to get, I'd also agree that dropping a bigger spring in make sense now.

If it comes in over, then you can chop off a coil or just heat the end over a lighter until it just starts to glow and squish the final coil in, which will drop the power a little.

I can't find any information on the diameter of your barrel, only the length, so the other thing you might consider is a tighter bore barrel.  @ak2m4 is the go-to for gear, and while I'd normally recommend ZCI, I've also had good experiences with AOLS and have just dropped this (in-stock) 455mm into my DMR.

https://www.ak2m4.co.uk/internal-parts/inner-barrels/aols-aeg-inner-barrel-455mm

That's getting me a very decent 1.7 - 1.8J out of an M130 spring, which is slight more than you'd notionally expect.

I'm going by this listing of your gun which claims a 463mm barrel.  You should of course check, and it's fine to go shorter on barrels: once the puff from the cylinder runs out, the barrel is really just getting in the way.

 

[ak2m4]

I've been quite surprised by the AOLS, the longer barrels are phenomenally dirty inside though so need a real thorough cleaning.  They are lighter than the ZCI barrels, performance so far in the 10 or so I've tested is identical.  I've run a snake cam down one and again comparable to ZCI.  Quite pleased with them as a backup product to ZCI, however not sure they are being made anymore.

 

[Speedbird_666]

I've been quite surprised by the AOLS, the longer barrels are phenomenally dirty inside though so need a real thorough cleaning.  They are lighter than the ZCI barrels, performance so far in the 10 or so I've tested is identical.  I've run a snake cam down one and again comparable to ZCI.  Quite pleased with them as a backup product to ZCI, however not sure they are being made anymore.

Click to shrink...

I think I might take a punt on an AOLS barrel to replace the tinfoil one in my son's G&G.

I Spent the last of this month's 'play money' on your site yesterday, so hopefully you'll still have some barrels in stock come payday.

Any sign of the ZCI consignment?

 

[ak2m4]

Any sign of the ZCI consignment?

Click to shrink...

thanks man.  ZCI is stuck in FedEx customs clearance at Stanstead since Sat for some reason.  

 

[Rogerborg]

Yup, the AOLS I just got was pretty oily, but cleaned up nicely.  Accuracy is unknown, but the 110mm in my MP5K is fine, and they both do a good job in keeping the puff behind the BB.