unusual fps from upgraded spring

[Dirty Deeds]

POP can chrony is useless and will never give you an accurate FPS.

Gear timing is a myth.

Your problem lies with air sealing. Maybe D-Boys mech boxes have an issue with air sealing and they compensate with a stronger stock spring in comparison to let's say TM? I would take the D-Boys spring and put it into a TM mech box and see what FPS it gives. You may find that the D-Boys spring in a TM will give you over 400 FPS.

Just a theory, as I have no experience with D-Boys, however I have plenty of experience overall.

[m102404]

Pop can chrony = bad
Gear timing = just plain wrong (sorry, no personal offense meant)

If the AEG reliably shoots 330 with one spring and there aren't wild deviations between shots...then simply dropping in a stiff spring should result in a higher velocity.

Things that mess with this are:
1. You screw something up with the previously good airseal (but George swapped back to his "old" spring and got the original results)
2. You have an extremely long inner barrel for the cylinder that you're using
3. You have a short barrel for the cylinder that you're using.

While the Dboys stuff is utter junk and not worth the $10 of savings vs. good parts...once it's working, it should continue to work.

A stiffer spring will not alter the nozzle to hopup fit (although this can vary between assemblies...especially if you're not consistant with tightening the stock screw).

It's really odd, because if he's using the stock inner barrel length and it's a ported cylinder...simply dropping in a s120 should net a 60+ fps increase. 30-40 if it's a really sloppy setup.

On a non-linear spring the tight pack of coils go at the back. On a Modify S120 spring, IIRC it looks more like a linear spring (at least the two I have left are not easily identifiable as non-linear). I strongly suggest you try a Modify S110. Depending on the rest of your setup....that should put you between 360-390.

Or....put it aside as a backup...but a G&P complete mechbox. Sure it costs $200 or so...but 2-3-4 evenings struggling with a problem mechbox that you end up with little to no confidence in, sure makes it seem worthwhile.

[georgehutchison]

I am going to try my g&p box today with the s120 then the d-boys spring. this will narrow it down if its a hop-up airleak issue. Then I will try my d-boys box in my g&p to see how that works. At least I am lucky to have a bunch of m-4's so I can do some testing with various parts. Thanks everyone i will let you know tonight what happens.
George

[Corleone]

I knew I was in for it when I wrote the whole gear timing part, but seeing as I spent so much time just narrowing down the problem, and comming to just that conclusion, I thought it was worth mentioning. It was the case on my friend's v2 gearbox (VFC HK 416), where he first got +-280 FPS on his new Systema 1J spring, and then when setting the gear timing differently (and only gear timing I might add) getting 330-340 FPS. We did this cause we both suspected that the nozzle was being pulled back before the piston slammed into the cylinder head. I also had huge problems getting my Echo1 P90 gearbox firing the BBs properly. It would not propel the first BB, but instead shoot two at a time every single time o.0 When test firing the gearbox outside the gun, it became apparent that the nozzle didn't position correctly. If any1 think it's an airseal problem, or that I changed multiple things at a time, save yourself the trouble. I was spending half a day just trying out different gear timings, and finally it would fire correctly. Now it shoots consistently 360-370 FPS, sadly way more than I want from the gun, so I needed to cut the spring a little.

The nozzle to hop-up seal was merely a side note, because it's a classic thing with the AR-15 series of guns. It will of course not fix this problem mentioned by George, but it's worth mentioning to everyone that cared to buy an Armalite. Please note that it's not for sealing between the hop-up unit and the gearbox, but the nozzle and the hop-up rubber sleeve. Buying and airseal nozzle might not give much of a performance jump, of course all depending on the quality of George's dboys nozzle.

[CDN_Stalker]

What's wrong with having an AEG that shoots ~350fps? Seriously, it's pointless to upgrade to 400fps, and most often than not, will hinder performance out of most AEGs. Some will benefit large, most are very happy in the 350-370fps (w/0.20g BBs) range, even when using 0.28g BBs.

[Corleone]

Originally Posted by CDN_Stalker

What's wrong with having an AEG that shoots ~350fps? Seriously, it's pointless to upgrade to 400fps, and most often than not, will hinder performance out of most AEGs. Some will benefit large, most are very happy in the 350-370fps (w/0.20g BBs) range, even when using 0.28g BBs.

Good point! Besides there are restrictions too. Over here in Norway there's a maximum of 350 for full auto, and you should try to be careful when playing. You're also not allowed to use more than 300 FPs indoors, meaning that you can't enter a building without drawing your secondary. I'm more than happy around 1J, or 330ish, which I see many overseas playsites have set as their max limit (overseas meaning at your side ).

EDIT: Fixing all the possible airseal-leaks can quite possibly get the gun a lot higher on the FPS alone. That way you can actually get a weaker spring and make the gearbox last a lot longer. This is espcially the case with v2 gearboxes, that really need the relief it can get.

[yuhaoyang]

I think it's just that putting a 400fps+ spring in a mechbox and having it only shoot 350 creates damage and a drop in rps that can be avoided by fixing the air seals

[Corleone]

Originally Posted by yuhaoyang

I think it's just that putting a 400fps+ spring in a mechbox and having it only shoot 350 creates damage and a drop in rps that can be avoided by fixing the air seals

Echo?

[georgehutchison]

So heres where I am so far. I dissasembled another long m4 today to try this s120 spring. came out at 390 fps w/.20's so its not the spring.
Next I installed the g&p mechbox into the d-boys gun with the d-boys barrel and hop up. =390 fps.
so its not the hop up or barrel. Great seal in the hopup as i have allready checked it for leaks.

Next I installed the back to stock d-boys mechbox into the g&p AEG and it shoots 350 fps. Same readings as with the d-boys barrel and hop up.

I then installed a modify s120 in the stock d-boys mech box and got around 330fps in both G&P and d-boys guns.

So far i have narrowed it down to being some issue with the d-boys mechbox with a longer spring. Can't see how as it makes no sense at all. I think i will leave the d-boys mechbox stock spring in and just instal bushings and shim it.

As far as wanting higher fps, I use .28 ammo at our outdoor field and found that extra 50 fps gives me a small advantage in range. My G&P is fully done up and can handle 400 fps with no issues. I use it on semi auto only and run it more as a countersniper setup.

I agree that 350 fps is usually enough and I use many other guns shooting at that fps for most applications.
I am going to do a little research on d-boys and see if other players have done setups on thier mechboxs. I will post back

[CDN_Stalker]

You know that once I set up my CA M24 to shoot around 340fps using 0.20g BBs, and when tweaking the hop up I was able to get my 0.30g BBs out to around 280-300ft rather easily. Just saying, fps helps but can actually reduce the range if too high. Currently I have it set up for around 400fps and am really happy with the way it shoots the 0.36g BBs for range and consistancy. And my MP5SD I recently downgraded to 360fps from 400fps since at 400fps it sucked using 0.28g BBs, but is much happier sitting at 360fps, same as my MP5A5 when it shot the same (which now sits at around 300-330fps, have to check it again).