A new hybrid system for a 1:1 VSS build

[Dimitri MdP]

Hi guys, 

I've something in my mind, and considering I don't have the money or resources to make it at big scale on my own, I thought I would share it to see what you think.

I've always been a big fan of the VSS Vintorez. That silent, deadly, sexy soviet widowmaker...  


Unfortunately, when some Airsoft companies finally released their versions, they decided to deform it beyond recognition to fit the gearbox of those horrendous Scalextrics people call AEGs. Specially LCT. Like... WTF LCT... really??


Can't help but hear that poor thing screaming for a mercy kill  

 

So going back on topic, I was hoping for a GBB company to make it into an awesome 1:1 GBB... To be honest i thought it would be no time before we get a GBB version, albeit deformed too, as we all know they are lazy bastards that will just take AEGs bodies and clone them, just replacing the gearbox for a GBB system, inheriting all deformities.

But years later there's still no sign of such thing, so I was even considering making my own, perhaps from an AEG body frankensteined together with some WE spares and some custom made parts. While I was at it, I found there's another good reason no one has made a GBB VSS yet.... This video shows an awesome animation of all the parts, and (at 1:03) how it functions. 

 

If you're paying attention, you'll see that unlike 99% of modern rifles, and 100% of GBBRs, the real VSS / VAL / SR3 plaform is not hammer fired, but striker fired.  So there's a big metal rod right were the nozzle and blowback unit would be positioned in pretty much all GBBRs, which will certainly prevent using any traditional platform.

That really slowed my progress. A LOT.

But then I thought... what if instead of trying to use an existing system, I could develop a new concept for it... and after the 100th time watching that video at 25% speed, it struck me: We could use simply use the striker pin as a piston and the bolt carrier as as cylinder. That pretty much leaves us with an awesome, spring-powered VSS with somewhat realistic internals. Sears and all internal parts will still look and function like the real thing, with the only difference being that instead of hitting the primer, the striker will compress the air needed to expell the bb :D

But being the GBBR addict I am, that was clearly not enough for me. So I thought of a new system:

Using the rear part of the striker (the one that engages with the sears) to hit a gas release valve of a typical GBBR style mag, we could have the power to send the bolt back. But where would I send the gas if the bolt carrier and firing pin are used as a cylinder and piston?? Easy: the real gun gas piston, with an Oring and such to provide good seal. Routing the gas there is the hard part, but once that's solved, it should be perfect to build pressure in the gas chamber sending the bolt back, which in turn will release the magazine's gas release valve, cutting the flow.

That way the firing sequence would be an hybrid, with the bb being propelled by compressed air like in a spring-powered airsoft gun, and the blowback powered by a gas-in mag system, which will provide the perfect consistency of spring guns with the awesome kick and cycle of GBBRs, while keeping cooldown at minimal, as I'd be saving all the gas that is normally used to propel the bb.




Now I think I got all pretty much figured out. I might start from a VSS model as sold by NPO AEG (if anyone knows how to source one of those, that'd be great) that, while not being a true 1:1 to my eye, it certainly looks less deformed than any AEG body. 

Then make a custom striker / piston (pretty much a striker with a piston head instead of a needle in front) and a bolt carrier / cylinder (just a solid bolt carrier with a hole in the correct diameter for the piston and a typical GBB feeding nozzle). Using a WE AK type hop unit for awesomeness, coupled with WE AK feed lips and some 3D-printed midcaps. And of course, Maple Leaf Autobot bucking + ML inner barrel. perhaps in the super-short real barrel length to keep the ability to carry in his own little suitcase for added awesomeness. 


At that point it will be an awesome springer. Then perhaps I could use the upper third of WE AK magazines to provide the gas needed for blowback. The hard part here is finding how to route that gas to the front of the gas piston. I was thinking perhaps a gas coupler valve like the one in WE P90 magazines, that would engage when the mag clicks in place. But that might be a pita with the angles... Then it's just a little line routing it to the piston, and making sure it seals properly and releases the contained gas when the bolt carrier reaches the back, resetting the striker / piston to the sears.


If I somehow manage to fix that, then making it work would be easy as adding something to actually hit the gas release valve when the piston sets forward.. A firing pin housing fixed to the receiver like that of the WE SVD is the obvious choice to me. 


Anyway... what do you guys think about it?  I really don't have the money to make the build right now, so there's time for thinking this all the way. Any input is greatly appreciated.

(and if some manufacturer reads this and decides to stole the idea... you're welcome to do so just remember to return the favour sending me one if you're kind enough )

[renegadecow]

The way I'd do it is to use pistol mags inside the mag shell occupying the front area. The back, or at least what is immediately behind the output valve is hollow to accommodate a traditional hammer and valve knocker assembly which is mounted on the gun. The bolt remains the traditional setup and the only down side is you see the hammer assembly if you look up into the mag well.

[Dimitri MdP]

Just received a reply, clearly google-translated, from NPO 

 

The model is almost a 1:1 replica they built for museums and such. It's built to order, takes a month, and costs about 500USD, payed 50% upfront and 50% before delivery. 

 

That's a little more expensive than I thought it'd be, but if I get lucky with job projects the next months I might be able to get it and start working on the mod.

 

BTW if anyone needs a web developer....

[Roland1014]

That's not how I would go about it, from an engineering standpoint.

[Dimitri MdP]

That's not how I would go about it, from an engineering standpoint.

Any input would be appreciated. 

[Roland1014]

It will be very difficult to create a system that will be able to strike the valve and then be timed properly to disconnect the valve knocker, if you want to stay true to the striker fired concept. Even airsoft Glocks are hammer fired.

[Roland1014]

I would use the blue as the striker sear, the red as the trigger disconnect/FA sear (both of these are the actual function), but design the yellow as a GHK-esque empty mag indicator to hold the striker back even when the trigger is pressed. I would use a mag designed around Devilhunter's R&D and work with Volante to maximize nozzle capacity since you have a decently large bolt. The inner barrel would be like the real one and only go to the end of the ported outer barrel. On CO2 and using a Volante nozzle with a 6.01 and good VSR hop you should be getting excellent range and power, and phenomenal recoil. Your main two issues will be ensuring the suppressor is concentric to the bore and designing a valve knocker that is disconnected by the bolt return.

[BigAl]

Don’t see the point of complicating it, like previously said airsoft Glocks use a hammer, no one ever complained about it. It works it looks good, end of.

[Roland1014]

Don’t see the point of complicating it, like previously said airsoft Glocks use a hammer, no one ever complained about it. It works it looks good, end of.

If I had some dimensions I would draw it up. This would be more simple than a Glock, and would allow the parts to be beefier too. 

[Dimitri MdP]

It will be very difficult to create a system that will be able to strike the valve and then be timed properly to disconnect the valve knocker, if you want to stay true to the striker fired concept. Even airsoft Glocks are hammer fired.

My plan about it was just adapting the length of the striker in such way that in the "fired" position, the back part of the striker  (which would be the one hitting the valve knocker) rest a couple of cm behind of the bolt carrier. That way it will not be 100% realistic, but allow the bolt to engage the striker back at the correct timing for proper gas disconnect. 

 

I still have to make the exact measurements and calculations, as I can see the elongated striker / piston messing with my cylinder volume, but a priori I think it could work.

[W1dget]

I want to start off by saying the design is cool as *fruitcage*, to me anyway. The idea of using the gas tube for its intended purpose is just cool. That being said, you have a limiting factor which is, as far as i can see, unaccounted for.

 

Gas in mag systems are limited by volume and pressure of the gas. I think its safe to assume you don't want to walk around with a 3000psi bomb in the bottom of your gun (not to mention it wouldn't be practical for sealing) so lets assume that your working at regular propane pressures. Most companies (lets exclude daytonagun and escort for instance) understand this limitation and that is the reason why the common in bolt BBU is used and retrofitted into so many ggb's. Long story short it uses and amazingly low amount of the available pressure to cycle the bolt.

 

I dont know what FPS youre aiming for but go grab a GBB and compare how the recoil spring with the firing spring even a stock 280 fps VSR. The VSR needs FAR more force to cycle it.

 

Now with your design you are going to have a massive gas efficiency problem. You are going to use at least 10x more gas per shot through pressurising the entire gas tube system just to cycle and needing far more pressure before the spring is compressed and the gas is cutoff.

 

I'm going to let this idea stir for a bit, See if i can come up with any improvements.

[Dimitri MdP]

Yup the spring tension might be an issue, specially since the recoil spring tension will be added to the piston spring. I'm not aiming for a particularly high mark though, just about 420FPS, and I know stock standard VSR springs can reach 500 FPS (with a tightbore, and extending the porting and removing the limiter in the cylinder), so power spring will be somewhat lighter than that. 
Also I'm hoping to address that issue trying to keep as much gas as possible in the gas tube between shots instead of dumping it all as any GBB does as soon as the nozzle disconnects from the chamber.  

To be honest this is my #1 concern, #2 being balancing all those forces, pressures and volumes in the system. I might develop a proof of concept for the recoil system before building it into the gun, as the base model is pretty expensive for a dead end.

But anyway, If everything else fails, I'll probably just go with a traditional GBB style and find a way to hit the valve without the striker/piston idea.

[renegadecow]

Using those light valves by Maple Leaf and A+ would help tremendously. They only require little pressure to open so your striker spring doesn't have to be anywhere near as heavy as a VSR's.

[Dimitri MdP]

Using those light valves by Maple Leaf and A+ would help tremendously. They only require little pressure to open so your striker spring doesn't have to be anywhere near as heavy as a VSR's.

You are missing the point

 

The striker will be working as a piston and the bolt carrier as a cylinder, so the bb will be propelled kind of like a BASR, using gas only for the blowback.

The striker spring will be the piston spring. So the output energy ("fps") will depend on that spring's strength.

[renegadecow]

Oh, well, that's gonna be a tall order. Even 200fps Marui spring pistols have a heavy spring which I highly doubt a gas piston system of that size will be able to cock, much less something the likes of a VSR spring.

[Dimitri MdP]

Gonna make a proof of concept soon. If it works, I'll order the base gun and the biggest challenge left would be to route the gas to the piston. If it fails, plan B is going back to the drawing board and try to achieve the "striker fired" ish concept hit the valve... without an actual striker occupying the bolt.

[Brigg]

There are plenty of Airsoft guns which use a striker or firing pin to strike the valve.

 

They are the cheaper end co2 gbb pistols that wingun and similar companies put out. They have a different magazine layout where the release valve is directly behind the BB in the magazine.

 

That would likely be easier to use the trying to have a setup that routes gas forward and the up the gas tube. If you're really set on a striker that is.

[mezurashii]

 

Just received a reply, clearly google-translated, from NPO 

 

The model is almost a 1:1 replica they built for museums and such. It's built to order, takes a month, and costs about 500USD, payed 50% upfront and 50% before delivery. 

 

That's a little more expensive than I thought it'd be, but if I get lucky with job projects the next months I might be able to get it and start working on the mod.

 

BTW if anyone needs a web developer....

 

When you say it is a 1:1 replica I assume you mean externally? Or is it a model gun that is 1:1?

[Dimitri MdP]

When you say it is a 1:1 replica I assume you mean externally? Or is it a model gun that is 1:1?

It's a non-working 1:1 replica to display in museums and such. Non-working and unable to be converted for real firearms use, etc.  But it's a great base for a GBB project, unlike AEG VSS bodies that are horrendously deformed. 

 

BTW, I've running some test and it seems you guys were right, compressing a normal m110 spring required A LOT of gas. By now I'm pretty sure I'll discard the hybrid idea and just use the body with regular GBB internals based on the WE AK platform, as I already have lots of spare parts and magazines available to make the conversion. Hopefully I'll keep the striker-fired idea somewhat.. just got to think this through a little more.

 

 

[mezurashii]

It's a non-working 1:1 replica to display in museums and such. Non-working and unable to be converted for real firearms use, etc.  But it's a great base for a GBB project, unlike AEG VSS bodies that are horrendously deformed. 

 

BTW, I've running some test and it seems you guys were right, compressing a normal m110 spring required A LOT of gas. By now I'm pretty sure I'll discard the hybrid idea and just use the body with regular GBB internals based on the WE AK platform, as I already have lots of spare parts and magazines available to make the conversion. Hopefully I'll keep the striker-fired idea somewhat.. just got to think this through a little more.

 

 

So it is more or less just a 1:1 shell of the VSS then? Could you give me a link to it? 

[Dimitri MdP]

So it is more or less just a 1:1 shell of the VSS then? Could you give me a link to it? 

 

 

http://npoaeg.ru/maketvss/

[Schaap]

I'm intrigued by your approach.

I don’t think there is a “gas cocked, spring fired” airsoft replica on the market.

 

Oh, well, that's gonna be a tall order. Even 200fps Marui spring pistols have a heavy spring which I highly doubt a gas piston system of that size will be able to cock, much less something the likes of a VSR spring.

 

Yes, but that is only because people are weak creatures.    Don't forget gas pressured cylinders pack a lot of strength. Just look at how hard the bolt of a GBBr (and some are pretty hefty) is recoiled... That takes some force too.

 

Anyhow, I decided to do some basic math, just to see if it can be done.

Given:
BB Energy: Ebb = 1 Joule
Spring constant: k = 5N/cm
Energy losses (piston friction, heat loss by compression of the air,...). No idea, but I estimated this at approx. 50%
Total required energy: Epot = 1,5J
-> In this simple calculation, we'll consider the gas piston return spring to be of marginal influence (like 1/5 - 1/10k)

Calculation:
Epot = 1/2 . k . dL²
<=> dL = ROOT( 2 . Epot / k)
dL =~ 7,75cm ; this is the length the spring needs to be compressed to have the required potential energy.
F = k . dL = 39N ; Means you'd have to pull approx. 4kg on the cocking handle. Sorry... No VSR here to check 

Assuming we use a 12mm diameter piston:
A = d² . Pi / 4 = 0,000113m²

Maximum pressure required to fully compress the spring:
p = F / A = 3,4 bar

 

Now, gas volume...

V = A . dL = 0,00000876m³ of gas, assuming at 15°C & 3.4bar
- Equals 0,00003m³ of gas at 15°C, 1bar (p.V = m.R.T)
- Expansion ratio of propane liquid-to-gas is approx. 305.9
- Specific weight at boiling point, 1bar: 580.88 kg/m3
=> Doing the math, sums up to be approx. 0,06g of gas per cycle. A Coleman propane bottle fits 465gr of gas, so that's almost 8.000 cycles.

^{Now, the volume calculation is off, because it makes a lot of assumptions that aren't correct.
When designed correctly, I'm pretty sure it could work. But it will be a lot more difficult and expensive, with no actual benefits in the end (apart from a slightly more realistic design).}
 

[Dimitri MdP]

Thanks for that awesome reply.  Gotta take 2 or 3 extra readings to process that information lol 
 

But it will be a lot more difficult and expensive, with no actual benefits in the end (apart from a slightly more realistic design).

The main benefit is the consistency of a piston powered system, far superior of those powered by gas. Which is a great addition for a precision rifle. Typical variation in spring powered guns is +/-1 FPS, while on gas is more like +/-10 with some really odd high and low peaks. 

I'll have the time to make some realistic-ish proof of concept in a month or so. So this is a slow project, but I'll eventually get there.