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TrevorJW

Echo 1 Platinum Edition M4 FPS/Range Problem

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So I'm a reasonably experienced tech, there really aren't any guns I haven't been able to fix. Enter the echo 1 platinum edition m4, owned by one of my friends on my airsoft team, which he absolutely loves and adores. My friend comes to me saying there's an fps/range problem (normal fps is 370-400). I open up the gun, and the gearbox is literally the most pristine stock gearbox I have ever seen (auto shim, o-ring nozzle, good grease, great compression, etc.). I take a look at the hop up, and no problems there either. so this leaves me basically stumped. I put everything back together and fire a few rounds, chrono it (shooting INCREDIBLY low, around 280 or so,) and then the piston strips. One thing I did notice was that the gun sounded kinda like it was halfway to being jammed. So we get a new piston (http://www.evike.com/products/38172/) and the seal is still great, and I check the nozzle's seal with the bucking, everything is all good. Shoot it, chronos 280. Clean the barrel, 300. Different bucking, 300. Shave the tappet plate, 300. New madbull 6.03 tightbore barrel, 300. Different gearbox shell, 300. New hop up, 300. Same gearbox shell, 300. Old barrel with new hop up, 300. At this point I've ruled out pretty much everything that could be gearbox related, so I focus more on the hop up/ barrel, and find everything to be in order. So now I'm completely stumped. My friend is about to order a prowin, and if I can't figure it out by then, he's probably gonna get a new gun. Any ideas or suggestions?

Edited by TrevorJW

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Definitely not the spring, the gun's only a couple months old and the spring looks to be completely in tact. However I did swap it's barrel with another gun and it functioned in the other gun just fine, though my friend's gun had the exact same crappy 280-300 fps - which leads me to believe that there might be a fracture in the air nozzle.

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Fracture in an air nozzle is not going to exhibit that much of a FPS loss.

 

"Tired" does not mean it is broken or fractured, which means it will be intact. It means it has lost tension.

 

If your friend left his spring compressed for 2 months...yeah it can lose that much tension to drop lots of velocity. Especially if it is a low grade alloy spring, a soft spring...or both.

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Fracture in an air nozzle is not going to exhibit that much of a FPS loss.

 

"Tired" does not mean it is broken or fractured, which means it will be intact. It means it has lost tension.

 

If your friend left his spring compressed for 2 months...yeah it can lose that much tension to drop lots of velocity. Especially if it is a low grade alloy spring, a soft spring...or both.

He used it just about every weekend before the incident, and almost always uses semi. He and I both know very well not to leave a spring compressed and we always fire a couple shots on semi before storing our guns. And the spring is pretty high quality. Another thing that might be good to mention is that the gearbox is originally manufactured by vfc.

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He used it just about every weekend before the incident, and almost always uses semi. He and I both know very well not to leave a spring compressed and we always fire a couple shots on semi before storing our guns. And the spring is pretty high quality. Another thing that might be good to mention is that the gearbox is originally manufactured by vfc

 

And Airsoft is a high precision industry with warrantied items?

 

In all seriousness...it can be the spring. And how do you know it is high quality?

Edited by Guges Mk3

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And Airsoft is a high precision industry with warrantied items?

 

In all seriousness...it can be the spring. And how do you know it is high quality?

Well there's obviously no way to know FOR SURE, but the gearbox is literally the best stock gearbox I have ever even heard of. It includes auto shim gears, had a great shim job on the bevel gear, and even had an o-ring seal plastic nozzle. I honestly doubt that they'd put a crappy spring in a gearbox that is so amazing. I guess I'll take a look anyway, maybe swap in one of my spare m110 springs.

Edited by TrevorJW

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the thing is I have an m249 made by a&k, and recently I opened up the gearbox just for a check up to find that the spring had broken in three. The funny thing is I had only lost about 10 or 15 fps, so that kinda leaves me thinking that a "tired" spring couldn't have that much of an impact on the gun's performance.

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the thing is I have an m249 made by a&k, and recently I opened up the gearbox just for a check up to find that the spring had broken in three. The funny thing is I had only lost about 10 or 15 fps, so that kinda leaves me thinking that a "tired" spring couldn't have that much of an impact on the gun's performance.

So you assume every spring will break, or wear in the exact same way based on your experience with one gun?

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So you assume every spring will break, or wear in the exact same way based on your experience with one gun?

Not at all, and I am checking the spring in a few minutes (been busy with new years parties and stuff like that). The thing is it seems the problem appeared rather suddenly, within a week probably. Could a spring weaken that quickly? Btw the gun originally chrono'd 400 and the fps dropped to 315 within a week.

Edited by TrevorJW

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So how much money did you waste before you replaced the spring?

 

I haven't spent anything (other than countless hours of my time), though my friend (who owns the gun) has spent about 20 bucks (new hop up and new piston because the old one got stripped). I have so many spare parts lying around that I rarely need to purchase anything.

Do you have a different gearset you can try out? That may be the source of the strange gearbox sound, also might be problem with the sector chip/cam causing the seal to be off, even with perfect compression.

 

It's definitely not the gear set, though I am beginning to have second thoughts about the validity of my spring swap test. I'm taking the thing apart right now and I'm gonna swap springs with a king arms v2 gearbox (chrono's 410-420, guessing the spring is m115; it's not quite as long as my settled m120) that I fixed semi on for another friend. I'll take a look at the difference between the 2 and I'll post back afterwards.

 

Edited by airborne101

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It's definitely not the gear set, though I am beginning to have second thoughts about the validity of my spring swap test. I'm taking the thing apart right now and I'm gonna swap springs with a king arms v2 gearbox (chrono's 410-420, guessing the spring is m115; it's not quite as long as my settled m120) that I fixed semi on for another friend. I'll take a look at the difference between the 2 and I'll post back afterwards.

If it's shooting 410-420fps, then it is much more likely an M120. Springs come in different lengths and it is no indication of the power.

 

Also, please do not double post. Rather use the Edit and Quote buttons.

Edited by airborne101

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Check the bushings/bearings. I had my sector gear bushing fracture into many pieces and the pressure from the Piston caused it to move and slip. The piston was then released early which caused the feet per second drop.

Make sure you check the top and bottom. Over time you get used to just lifting the shel up and not looking at the other half so it's possible one could be broken, or 1/3 fell out but the grease kept the others stuck in. Then when you shoot the gun it releases early.

Edited by MrGearbox
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