Possibly, but I should be able to do so without using an ETU, correct?For semi-locking, do you plan to fit an ETU like the Perun Hybrid into your budget?
If I knew what I was doing and am able to--this time-- correctly reassemble the gearbox, I would be willing to open it up. It's not a refusal to open it, but I am very hesitant because, as said earlier, I basically destroyed the last gearbox I opened.You will need to open your mechbox and change something that looks like this:
View attachment 283402
Which entails a complete tear down of the mechbox. Of which you stated that you don't want to do...thus you will not be able to put together a custom DMR....
my understanding is that the DMR must be mechanically restricted, so you will need to figure out how to keep the gearbox from going into a full auto mode, some sort of t’ournament lock’ so you won’t be able to reverse it while playing. They do the same thing with HPA regulators, needing to be tournament locked so you can’t change the air pressure during the game. I havn’t had to figure this out yet, since my DMR uses a mechanical trigger instead of a ETU, but it can be as simple as adding a grub screw to block the fire selector lever, I believe. (As always, check the rules before going, as different organizations have different ways, rules and expectations of players)Possibly, but I should be able to do so without using an ETU, correct?
I no longer have that specific gun, but I do have a spare that I could tear open. Having the extra experience of opening that gearbox would definitely help in putting together an SR-25 build.You can always start off by trying to fix that one
Full-auto must be permanently disabled, and only usable with complete disassembly and modification of the weapon.What does your field require exactly in terms of semi-locking?
I'm definitely gonna rip open that old gun first--now that I've remembered I have it--so I'm not completely oblivious when I open my next one. However, I'm fairly certain that my extra does not come apart like a normal gun. Which doesn't really matter since I'll just be getting familiar with gearbox work. Mostly, both of these will be learning experiences since, in the future, I want to be doing custom work on most of my guns.How set are you on the DMR build? You could very well do it and have it work out awesome, but if you're not confident about opening up the gearbox and doing somewhat finicky work, I would work on your extra before spending extra money.
If you wanna go for the DMR, we can help you flesh out a good parts/modifications list to start ya off.
Due to this industry having no standards what so ever.A list of goods parts and mods would definitely be a great help, and would be greatly appreciated.
An unfortunate truth, Guges.Due to this industry having no standards what so ever.
So very true...easily proven with Physics, mainly Fluid Mechanics/Dynamics...(Snip)
Contrary to popular opinion, having an o-ring on your nozzle doesn't help really, so I'd keep the stock nozzle. I checked out a review of this model, and despite the reviewer complaining about no o-ring, the gun still shot pretty consistently at the chronograph, even with the crappy BBs the reviewer used. (link to review: Review )
(Snip)
What's the reasoning behind recommending a metal hop unit? They don't perform any better than plastic... but I'm curious to hear what you think.I would recommend a few things
A: a good, strong metal hop up unit. Prowin for a budget, Maxx model hop up if you have the dough.
B: An R-Hop. While they are much more of a pain to install than a standard flat hop, they add just a bit more umph. Make sure to get a flat bucking, like Lonex of Modify Ryusoku.
C: Either a revamped compression system or an HPA engine. New compression system will keep your gun running as an AEG, and is more affordable. A Lonex compression system (piston, piston head, cylinder, and cylinder head), with a Maxx steel nozzle, is great. The HPA is going to be your best option, but way more expensive, so be prepared to spend. The Polarstar Kythera is a great DMR engine, since it only shoots semi and is fully mechanical, no electronics. But you will also need a tank/regulator/line set up and either a field that fills HPA tanks or a $300 compressor, so agin, deep pockets for HPA.
Finally, have a tech do a barrel/cylinder ratio for you to figure out your best barrel length.
Thank you.Okay, parts list here we go... Remember that it's very, very hard to guarantee fitment on anything, even if one has personal experience, and your Dremel should be handy! A chronograph is almost a must-have as well for gauging performance.
Before modding anything, you should always test the gun to see where you're at performance and accuracy-wise, and I'd suggest playing some game days with it as well to get a feel for it and where it's performing at, as well as what you want improved.
For my first round of mods I would do:
Full cylinder: any SR-25 or PSG-1 cylinder should do fine. Polish it up with some metal polish.
Check the compression by pushing the piston in without the nozzle on and holding your thumb over the cylinder head nozzle tube. If anything leaks, check the piston head o-ring and then the cylinder head for leakage.
You can regrease and stretch the piston head o-ring to improve faulty compression. Stretch it by putting it over the cylinder and heating gently with a lighter.
You can wrap teflon tape around the cylinder head to improve compression. That's self-explanatory.
You're most likely fine with everything else in the gearbox besides the cylinder. If anything looks funky, ask about it but don't buy a replacement at random.
Contrary to popular opinion, having an o-ring on your nozzle doesn't help really, so I'd keep the stock nozzle. I checked out a review of this model, and despite the reviewer complaining about no o-ring, the gun still shot pretty consistently at the chronograph, even with the crappy BBs the reviewer used. (link to review: Review )
Unless you have an issue with the stock trigger response, keep the motor and gears. If you want better response, a new motor is worth considering.
If you want to change the spring, Guarder is most likely your best option, as PDI springs are quite hard to find.
For the real magic, the hop unit and rubber, I would keep the hop unit stock, polish the barrel, and try out a couple of hop rubber and nub combos searching for good performance, as well as stabilize the whole thing. In my signature I have a detailed guide discussing hop rubbers, barrels, etc.
The biggest caveat on the Cyma SR-25 is that the ETUs are known to burn out, necessitating a replacement. You could either replace with a basic trigger unit, like one from Lonex or SHS, or go for a replacement ETU like the Perun Hybrid. Either will work.
In summary, here's the parts and mods I would personally start with, without having hands-on experience with the platform:
Hop rubber change or flathop
Barrel polishing
DIY nub and full barrel group stabilization
compression and shimming work only if necessary
full cylinder
And that's about all you need.
As a final caveat, all of your testing should be done using high quality BBs and using a good quality LiPo battery. In the USA, I would suggest BLS and G&G as your two most cost effective options. Krytac, Bushido, and ASG are also good options.
