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DSG FPS Inconsistency/Build Thread

8788 Views 176 Replies 9 Participants Last post by  Leo Greer
Hey guys, I recently have been working on a DSG build, but I've run into either one or multiple problems depending on if they're related. My fps is inconsistent on semi, fluctuating between 380-360 fps. On full auto, fps is even worse. One day it was around 360, so not bad. But the next day it was in the 250-300 fps range, so I don't know what happened there. Full auto shot pattern literally looks like a shotgun spread, though at least it is feeding.
Here's my parts list:

-18:1 stock gear set with shs DSG gear and stock tappet plate (<11mm)
⁃ shs high strength polycarbonate piston (SS + SC)
⁃ Matrix silent piston head (aluminum)
⁃ ASG 30k boost
⁃ Gate titan mosfet (dsg setting)
⁃ Maxx Model CNC aluminum hopup (pro model)
⁃ G&G hopup bucking (cold-resistant)
⁃ Matrix CNC aluminum air seal nozzle (ground off <.25 mm)
⁃ Matrix silent cylinder head (aluminum)
⁃ m150 spring
⁃ 265 mm inner barrel
⁃ ported cylinder

DIY mods done:
⁃ AOE
⁃ Shimming
⁃ Tappet return spring -4 coils
⁃ Everything greased/lubed accordingly

***tested with 11.1 v 2200mah 25-30c lipo and .20 gram bbs***

Most of these parts, including the hopup, bucking, nozzle, and tappet plate were used in my 12:1 SSG build, which worked just fine. I had this same problem with the SSG build but solved it by grinding <.25 mm off of the nozzle which made my fps more consistent; when it did change it was +-10 fps. Still using these parts, but encountered the same problem again albeit worse. I had already cut 2 coils off my tappet return spring, and then did the tissue test. Paper was blown off, so I thought that my nozzle wasn't returning fast enough. I then cut off 2 more coils. Paper moved slightly after that (but still quite noticeable on auto). So in total there are at least 4 coils cut off my tappet return spring and I'm still having the tissue kinda pushed off. At this point I'm even considering that the nozzle might be a hair too short (thanks to me grinding a bit off), causing hopup compression issues.

Note: This is my first DSG build, so by far I don't know everything. Any help is appreciated.
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Man, maybe I'm just lucky. Just checked all the cycle counters on my Titans. Nine titans, 4 DSGs, 5 SSGs, right at 1 million cycles combined, all SHS pistons, zero broken pistons, zero glue on the racks. Not including the other guns I have with no ETUs and SHS pistons and racks. I'm not saying don't use glue. I'm just saying I have not used glue and have not broke a piston on my guns or guns I put together for friends. Weird...
Man, maybe I'm just lucky. Just checked all the cycle counters on my Titans. Nine titans, 4 DSGs, 5 SSGs, right at 1 million cycles combined, all SHS pistons, zero broken pistons, zero glue on the racks. Not including the other guns I have with no ETUs and SHS pistons and racks. I'm not saying don't use glue. I'm just saying I have not used glue and have not broke a piston on my guns or guns I put together for friends. Weird...
sheeeeeeesh thats lucky
Man, maybe I'm just lucky. Just checked all the cycle counters on my Titans. Nine titans, 4 DSGs, 5 SSGs, right at 1 million cycles combined, all SHS pistons, zero broken pistons, zero glue on the racks. Not including the other guns I have with no ETUs and SHS pistons and racks. I'm not saying don't use glue. I'm just saying I have not used glue and have not broke a piston on my guns or guns I put together for friends. Weird...
what is your oppinion on the titans it must be high u have 9 OF THEM lol
what is your oppinion on the titans it must be high u have 9 OF THEM lol
All ETUs have their things, I happen to like Titan the most for V2 shells. You don't just drop in and screw down a Titan and it work perfectly in every setup. When you get them installed correctly they work well and have software that is useful for many things. Perun does not have that, Jefftron had issues with software on the old models. Not sure if Jefftron got that all sorted out with their new ETU. I personally don't like physical switches on ETUs, they have a much shorter lifespan vs an optical sensor. That is not to say optical sensors don't have their own set of issues though. I'm not a fan of Gate Support. Just preference of what you want to deal with really.
[mention]Jimps [/mention] are your SHS pistons the 14 tooth pre SS ones?
[mention]Jimps [/mention] are your SHS pistons the 14 tooth pre SS ones?
Yes. I then remove teeth that I don't need. Usually lighten the piston as much as I can. Under or at 20 grams total piston weight is what I aim for on high speed builds.
All right here's another update:
I figured my piston got wrecked because of PME and not bc of the SHS piston itself...turns out a guarder sp140 is not quite enough (that or my DSG is seriously inefficient). I tested with the crappy matrix m150 and I'm wondering if it was mislabeled? The sp140 should be stronger than the m150 right? The m150 was very consistent (1.43-1.46 joules on both a discharged battery and a partially charged one). When I tested the sp140, joules and fps dropped immediately, which made me realize I was getting mild PME. The SHS spring guide was no good for me either, as it wobbled too much leading to inconsistent fps. Does anyone know how thick the lonex steel spring guide is? SHS was too skinny for my guarder and crappy matrix + evike springs. Also, for those of you guys who pack big batteries, how do you avoid overspin (yes besides active braking)? And yes the matrix spring was only for testing...I'm going to have to order a stronger guarder one...

EDIT: I correct myself, the matrix m150 is indeed stronger than the guarder sp140.
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SP140 should be roughly equivalent to an m165 if memory serves, but irregular pitch springs don't get fully compressed with a DSG so usually you want to add a couple spacers to get a bit more compression. This also allows you to fine tune your FPS, although it is a bit tedious.

I believe I have a lonex spring guide in my parts pile, will measure after work unless someone beats me to it :) Will see if I can measure the Maxx guide as well, that one's been my preference for a while.
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Thanks, rm. I've run into an interesting problem: my fps is gonna be too high for indoor cqb at the rps I want to run at. I think I'd have to run somewhere around a guarder sp160 to keep PME at bay (using a fat battery). Currently with that matrix m150 my fps is around 350...
Its that dang battery lol. Does your 'fet have ROF control? Might be able to side step the issue that way... meaning no PME with the weaker spring,but FPS still low.
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Lonex spring guide, width at base / bearing: 11.25mm
Maxx spring guide, width at base / bearing: 10.75mm
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Yeah, I do have rof control...I think I will try that out. Thanks for that suggestion, wouldn't have thought about that myself. Also SHS steel spring guide shaft: barely 10 mm...
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Is your spring guide not threaded? How do you attach your buffer tube? When the screw is in the spring guide, it cant move around.

Oh, I see what you mean. Cant see how that would make a much of a difference. I have used SHS spring guides and not seen any issues with FPS variation.

If you use a bigger battery and get over spin, and then use a smaller battery and don't get over spin, that means the smaller battery is too small to use. It means the smaller battery cant supply what the motor wants. Never use a smaller mah/c battery to fix issues, that is why people say "lipos puff up". When you use the correct size lipo they will last a very long time. You can use a lower voltage battery though.
Krytac encourages use of underpowered packs to keep their AEG's from "overspinning".
Is your spring guide not threaded? How do you attach your buffer tube? When the screw is in the spring guide, it cant move around.

Oh, I see what you mean. Cant see how that would make a much of a difference. I have used SHS spring guides and not seen any issues with FPS variation.

If you use a bigger battery and get over spin, and then use a smaller battery and don't get over spin, that means the smaller battery is too small to use. It means the smaller battery cant supply what the motor wants. Never use a smaller mah/c battery to fix issues, that is why people say "lipos puff up". When you use the correct size lipo they will last a very long time. You can use a lower voltage battery though.
Actually you might have a point there...I've been testing without my stock screwed on which would anchor my spring guide better. I'll try chronoing with my stock screwed on...
Ok guys, I made some progress...I screwed my stock into my spring guide (like Jimps mentioned) and low and behold the SHS spring guide works just fine...I don't know why I never considered that (I get lazy when teching and usually don't assemble the entire gun as I know I'll be tearing it apart right after). Thanks rm and ben for the tappet advice, as my build is shooting very consistently, and FA has no fps drop...granted this is only around 35 rps. Something ain't adding up, I'm thinking maybe friction between the piston and gb rails. Also, I had a crazy idea to drill holes in the section of my tooth rack that's been short stroked (piston assembly is 17 grams)...would be nice if you could just cut the tooth rack off after the 8th tooth and then get a POM or polymer insert to slide into the remaining space to provide stability + reduce extra weight...I feel like my build should have a higher rof...maybe it's just the discharged battery I was using for testing but I would like to hear what you guys think.
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First, congratulations on getting a DSG running!

Low battery = low rps, particularly with a DSG as the spring is a lot stiffer and inertia isn't on your side. I've seen RPS literally double with a charged battery, be careful as you bring it up.

Does your Chrono track burst rps or do you have to shoot for ~1 sec for it to display? A longer burst of FA will pull the battery down harder, especially if discharged which will make rps seem lower than it actually is if you could clock 3-5 rounds. Also be aware parts wear in to some degree, expect a few rps gain just from using the thing.

Check piston rails by removing cylinder + spring and closing shell over piston, manually pushing it back and forth. It should slide freely, even feel a little sloppy. I know some folks swear against it but I've actually measured a ~5% rps gain from having bearings on both ends of the spring vs bearing and a spacer. YMMV, mind the weight, etc.

But congrats again dude! Happy tuning, now that it's working you need to break it and make it faster... that's the law :D
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Ok guys, I made some progress...I screwed my stock into my spring guide (like Jimps mentioned) and low and behold the SHS spring guide works just fine...I don't know why I never considered that (I get lazy when teching and usually don't assemble the entire gun as I know I'll be tearing it apart right after). Thanks rm and ben for the tappet advice, as my build is shooting very consistently, and FA has no fps drop...granted this is only around 35 rps. Something ain't adding up, I'm thinking maybe friction between the piston and gb rails. Also, I had a crazy idea to drill holes in the section of my tooth rack that's been short stroked (piston assembly is 17 grams)...would be nice if you could just cut the tooth rack off after the 8th tooth and then get a POM or polymer insert to slide into the remaining space to provide stability + reduce extra weight...I feel like my build should have a higher rof...maybe it's just the discharged battery I was using for testing but I would like to hear what you guys think.
What battery are you using? Specs? Which motor are you using? You went 18:1 and SHS DSG correct? Are you using a chrono for checking RPS or the Titan data?
[mention]Jimps [/mention] If you jump to the very top thread at the beginning of this post, you'll find my complete parts list...but yes, it's an 18:1 SHS DSG build and I've got a chrono...I feel like titan info is unreliable.
The Titan is very accurate on RPS. It counts the teeth on the sector. When using a chrono to calculate RPS you can be limited by feeding. If you are getting 35RPS on that setup, that means your 30k motor is only turning at 19k. So either voltage or resistance is holding you back. I would go off Titan RPS data vs the chrono. You can usually take 2-5k RPM off the listed RPM on a motor for account for load. Lower TPA motors tend to lose more RPM under load than higher TPA motors. 11k loss of RPM is a lot. I probably would not use that motor on a DSG personally. On my 20:1 DSGs I can get away with an 18TPA motor. Most times I use 22TPA motors, 16TPA is pretty low. Check voltage, try a different battery. Batteries will lie, not sure the brand you are using.
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