Airsoft HPA Dragunov SVU (With CAD)

This project was made possible by a hopup/barrel assembly designed by Wafzig, which I modified for use in the SVU. Check out his awesome airsoft projects:

https://cults3d.com/@Wafzig

A cad model of the dragunov svd by ehsan was used for reference, and in some cases modified parts are used.

This is the Dragunov SVU, or ОЦ-03 (OTs-03). It is a fully original build, and not a conversion for any existing gun. 

Please read through the entire text and look through all the pictures before starting this project so you know what you're in for.

It is designed for the Backdraft Phoenix HPA engine, though it wouldn't be difficult to modify it to fit a different engine (if not drop in, as it mounts to the front collar of the engine only).

It should be compatible with any Cyma SVD AEG compatible magazine as it was designed to fit a printed mag made to fit cyma aeg SVDs (more notes below).

I am releasing this as is, but I am including both the Fusion 360 cad file, and the step file for it. Refer to this cad as your instruction.

This is likely more complex than the typical printed airsoft builds (mosquito, PAAR15, etc). Soldering, adjusting fitment of parts (such as sanding filing and drilling) and troubleshooting will be required. Modifying the cad files for your own use may not be required but certainly is handy to be able to do.

Parts will also need to be oriented, and some will require support (namely the main receiver and the front receiver)

The major hardware required is:

• Backdraft Phoenix (or similarly sized HPA engine) with the v3 nozzle
• AEG inner barrel (i used a 510mm, 550mm should fit assuming you're filling the suppressor, up to 688mm ish if you go through the suppressor)
• AEG bucking
• 5/8" OD 3/8" ID Pipe x 20", Ideally aluminum or at least some metal (longer would work as well, just won't be accurate to the real gun)
• three microswitches (CYT1073/Omron D2F-5, clones are plentiful on amazon)
• B5B-ZR-SM4-TF(LF)(SN) connector (optional if you're okay with cutting your wiring harness)
• Misc M3 hardware. M4 bolts can also be used for the mag catch, that's what I used. 
• The mag catch will need a torsion spring, I wound one my self from piano/spring wire. 
• Voron Spec M3 heat inserts
  such as: here and here
• Some small pen springs for the folding sights and fire selector. 
• An m2 bolt is needed to retain the rear iron cylinder, optional if you use pic rail
• Two m2 bolts and nuts for the Hop Unit
• M3 set screws for attaching suppressor, gas block, and front handguard clip to barrel
• m2 bolt to secure the dust cover retaining lever to retaining shaft
• An optional m2 insert for the dust cover retaining shaft, there is a version where the bolt directly threads into the plastic.

Print Orientation: 

My pictures should be a decent reference for most parts. I designed the main receiver to be printed on it's top face to reduce the amount of support needed. The rear iron parts except for the mount were printed vertically. Front iron post i would recommend printing horizontally for strength. The handguard halves were placed with the face where the two halves meet parallel to the bed.

There are two files for the fire selector, one is flat and the other is “pre bent”. The flat one is meant to be printed as is, heated, and then bent to fit the gun. It will be far far stronger this way. I would also recommend putting some thread locker on the bolt that holds the fire selector so that the constant rotation of the selector does not back it out.

There are two files for the dust cover retaining shaft, one uses an m2 insert and the other direct threads into plastic. Be careful and thread the m2 bolt into retaining shaft before assembly, to make sure you don't strip it out.

Outer Barrel Modification: 

You will need to cut some notches in the pipe you chose for your outer barrel. The first one is where the barrel mounts to the receiver, it is likely overkill and you can chose to forgo it by removing the plastic that sits in the notch (the part is specifically the “Barrel Top Mount”). The next notch is for the bolt that goes through the front handguard retaining clip. I would recommend first assembling the handguard with both retaining clips, and then marking the hole on the barrel before cutting the notch. Make sure the handguard isn't twisted or anything. Refer to cad for how deep to make it. The last notches are for the gas block, where two set screws do the same thing as on the handguard retainer. basically just do the same thing here.

Wiring: 

The wiring is fairly simple, three wires come from the HPA engine's trigger board cable. An orange and yellow wire go to the trigger, on the way back to the FCU the yellow wire is interrupted by the microswitch for the safety. The fire selector is connected to the white wire, and the second wire for that switch connects to the orange wire, either on the switch its self or at the trigger board cable.

The wires for the fire selector and trigger run through the trigger linkage cover on the left side of the gun.

Make sure that that the fire selector and the trigger switch are wired normally closed while the safety is wired normally open

The pinout for the backdraft trigger board cable is: orange and yellow are trigger, orange and white are selector

You will need to bend the lever for the fire selector switch in a funky way similar to whats shown below, be sure to have extra microswitches as it took me a fair bit of trial and error. Alternatively, you can wire the safety selector to be the fire selector and remove the microswitch from the real fire selector.

Assembly tips: 

Refer to the hop assembly, and cad, for assembly of the hop unit.

The parts that you might have the most problem getting to fit is the dovetail where the front receiver and main receiver connect, for me it went together perfectly, but if your printer isn't especially well tuned it may not, and since its a dovetail it will most likely be quite difficult to sand to fit. I would recommend adjusting the cad model if you know you can't print that tolerance.  The next part is the threading on the suppressor, I had to adjust the thread once or twice based on some test prints, same thing applies here. Alternatively, you can just remove the dovetail, its overkill.

All bolts with the exception of the m2 bolt on the rear iron, the bolt that aligns the top HPA engine clamp to the bottom, the one that screws in from the inside of the receiver to lock the dust cover retailer, the bolt that the trigger rotates on, and the two bolts that secure the mag catch, will thread into either a heat insert or a nut. If there is not a slot for a nut, assume a heat insert goes there, double check in cad if necessary (any 4.7mm hole means heat insert)

Three heat inserts are put in the suppressor mount where the m3 set screws are used to secure it to the barrel.

Various parts have small holes in them for filament in order to lock those parts, such as the iron sight posts and the suppressor parts. You will likely have to drill them out first. On the suppressor I found they were not needed as the threads hold it tight enough.

The dust cover is retained in the same way as a real dragunov svd, assuming you assembled the retainer correctly, rotate it to point towards the muzzle to retain the dust cover, and point it in the opposite direction to release it.

The magazine shown here is this one by IAP. I didn't have much luck getting it past 50 or so bbs, but that's most likely a problem on my end, either way i would recommend off the shelf svd mags. If you choose to use his magazine, you'll have to cant the magazine to the side a little in order to clear the pistol grip when inserting it.

I left the suppressor hollow to be filled with your choice of material. This method just takes a bit of filament and seems fairly effective.