LCT VSS Issues

[JinxDuh]

Hey people,

 

I bought a VSS ages ago pre owned that had some issues with the hop unit (As informed by the seller)

 

I didn’t touch it for a while then decided to build it as a DMR.

I fitted a gate titan I had spare to semi lock it, gearbox works fine, compression all seems fine. I changed the inner barrel to a maple leaf 410mm (Using a 3d printed spacer to keep it central), a 70 degree ML bucking and one of the XT Omega nub copies & an XT M130 spring. 
 

The issue I’ve ran into is, if the hop is fully off it’ll fire at roughly 320 on .25g bb’s, roughly 280 with the hop in the middle, and with the hop fully on it won’t fire at all. I’ve tried the original nub and bucking, but it does the same thing. I also put the original barrel back in with both the upgraded parts and the standard - Same result and same chrono reading. At this point, I’m beyond lost on potential issues and where to look. 
 

This is my first DMR build too, so I may have missed a vital step and have no idea 🤷‍♂️😂

 

[JinxDuh]

My initial thought was the stock motor unable to handle the m130 and produce enough air/power, but I don’t have a spare motor to test my theory 😅

[Colin Allen]

14 minutes ago, JinxDuh said:

My initial thought was the stock motor unable to handle the m130 and produce enough air/power, but I don’t have a spare motor to test my theory 😅

If the gearbox is cycling, the spring will deliver the power that it is capable of minus any losses due to air leaks.

When you say that it does not fire, what do you mean?  Do you mean that it cycles but a BB does not whizz out of the barrel or do you means that the gearbox does not cycle?

If the former, do you expect it to with the hop fully on?  I have tried that with an AK and it usually jams.

[JinxDuh]

14 minutes ago, Colin Allen said:

it cycles but a BB does not whizz out of the barrel

Yeah, gearbox cycles and it does push BB’s in because if I pull the trigger 3 times then push the hop up to “off” and it’ll fire all 3 (Plus the fourth) out. 
 

I’m not sure if it’s common for BB’s to not fire with full hop tbh, I’ve never really messed about with the AK hop ups. My V2 hops do fire on full hop though. 
 

How would I check for air leaks? I’ve compression tested the piston parts and all seems good. I did notice the nozzle sitting a bit awkwardly though;

There’s a slight gap between the nozzle and rubber. Again, not sure if that’s normal.

[Colin Allen]

What you are experiencing is normal.  With the hop fully on, the BBs cannot make their bid for freedom and get jammed up; if you keep doing it, you risk damaging the piston/sector gear/tappet plate.

When the nozzle is fully forward, the tip should be in the lips (ooer, missus!)

To check the nozzle/rubber interface for air leaks, make sure there are no BBs in the chamber, turn the gun upside down, put a bit of paper over the feed tube and pull the trigger.  If the paper does a credible impression of a Russian tank turret, the nozzle and rubber are not sealing.  If it stays still or just moves a little bit, all is good.

[strykerles]

if the hop is fully on then the nub is pushing in too far for the bbs to get past, same thing happened with my cyma vss

 

looks like you may need to trim the lip on the rubber to eliminate any potential bbs catching on the lip

 

I used an asg ultimate m130 on mine and it fired out at 562fps on a .20, did the same thing as you and fitted a titan plus 18:1 gears and new compressions parts. standard V3 hop unit with ML 60, omega nub and standard 400mm inner barrel. changed to a m120 and dropped it to 490. with hop applied it fires .43s lovely and straight

 

I believe the battery goes in the suppressor on the LCT? on the cyma it goes in the stock, could the battery be pushing on your barrel maybe even with the  spacer?

[JinxDuh]

24 minutes ago, Colin Allen said:

When the nozzle is fully forward, the tip should be in the lips

There’s about 1/5 open area with the nozzle fully fowards, so I think that’s the next thing to remedy. Seems to be the likely culprit!

[JinxDuh]

40 minutes ago, strykerles said:

if the hop is fully on then the nub is pushing in too far for the bbs to get past, same thing happened with my cyma vss

 

looks like you may need to trim the lip on the rubber to eliminate any potential bbs catching on the lip

 

I used an asg ultimate m130 on mine and it fired out at 562fps on a .20, did the same thing as you and fitted a titan plus 18:1 gears and new compressions parts. standard V3 hop unit with ML 60, omega nub and standard 400mm inner barrel. changed to a m120 and dropped it to 490. with hop applied it fires .43s lovely and straight

 

I believe the battery goes in the suppressor on the LCT? on the cyma it goes in the stock, could the battery be pushing on your barrel maybe even with the  spacer?

 

Aye, battery goes into the suppressor. I have a battery cradle I 3d printed to hold the battery off of the barrel (That also acts as a second barrel stabilizer). Starting to think I'm paranoid about barrel stabilization... 

[Colin Allen]

43 minutes ago, JinxDuh said:

There’s about 1/5 open area with the nozzle fully fowards, so I think that’s the next thing to remedy. Seems to be the likely culprit!

Yep!  That would seem to be an issue.  I have just looked at the lad's one and the nozzle is fully engaged with the hop rubber lips.

 

Edited June 1 by Colin Allen

[JinxDuh]

1 hour ago, Colin Allen said:

Yep!  That would seem to be an issue.  I have just looked at the lad's one and the nozzle is fully engaged with the hop rubber lips.

 

 

Would it be at all possible for a measurement on the nozzle fitted? I have a sneaking suspicion the guy I bought it from has messed with it prior, as the one I replaced had 0 air seal and was about 1/2 the size of the one I fitted to test. No worries if not of course, as they're not the easiest things to get too!

[Shamal]

No.

[Colin Allen]

1 hour ago, JinxDuh said:

 

Would it be at all possible for a measurement on the nozzle fitted? I have a sneaking suspicion the guy I bought it from has messed with it prior, as the one I replaced had 0 air seal and was about 1/2 the size of the one I fitted to test. No worries if not of course, as they're not the easiest things to get too!

That would involve stripping it down.  I believe it is a standard LCT nozzle, which should be 19.7mm.

Edited June 1 by Colin Allen

[JinxDuh]

3 minutes ago, Colin Allen said:

That would invoice stripping it down.  I believe it is a standard LCT nozzle, which should be 19.7mm.

That's what I was thinking haha! I'll get a replacement ordered and hopefully it'll fix my issues. Thanks!

[Colin Allen]

Are you going to AP tomorrow?  If you are, I can bring an LCT nozzle.

[JinxDuh]

1 minute ago, Colin Allen said:

Are you going to AP tomorrow?  If you are, I can bring an LCT nozzle.

No bud, not out playing until the 9th (Next weekend) at Splatoon 🤙 Appreciate the offer though! 

[Colin Allen]

3 minutes ago, JinxDuh said:

No bud, not out playing until the 9th (Next weekend) at Splatoon 🤙 Appreciate the offer though! 

The lad and I might be there next weekend.

[JinxDuh]

2 minutes ago, Colin Allen said:

The lad and I might be there next weekend.

I'll keep an eye out for you!

[Shamal]

1 hour ago, Shamal said:

No.

Only joking. I've had a beer 😉

[JinxDuh]

The hop rubber that came out on the left, “standard” in the middle and a maple leaf on the right. 
 

I wonder if that’s a potential causer of the air leak? 

[Lozart]

If anything the lips on the ML rubber are longer than the OEM one. I highly doubt the overall shorter length is causing a leak though.

[JinxDuh]

9 minutes ago, Lozart said:

If anything the lips on the ML rubber are longer than the OEM one. I highly doubt the overall shorter length is causing a leak though.

Just trying to give myself hope 🤣 I ordered 2 new nozzles from ak2m4, I’m going to try the original rubber and test it - Mostly as something to do 😂

[Lozart]

Just for my own edification - at 280 fps on a 0.25 you would be getting 1.82J. What are you aiming for?

What cylinder are you using?

[JinxDuh]

I’m trying for around 410 FPS, on the stock rubber I just chrono’d it at 259.5 (Highest, hop fully on) and 162.5 (Lowest, hop fully off) with it being 239.5 in the middle (With a variation of 1 roughly, it was like .7, .1 etc) - This is on .25g BB’s

 

Chrono is suggesting that at 239.5 fps it’s 0.666 joules

 

 

[Lozart]

27 minutes ago, JinxDuh said:

I’m trying for around 410 FPS, on the stock rubber I just chrono’d it at 259.5 (Highest, hop fully on) and 162.5 (Lowest, hop fully off) with it being 239.5 in the middle (With a variation of 1 roughly, it was like .7, .1 etc) - This is on .25g BB’s

 

Chrono is suggesting that at 239.5 fps it’s 0.666 joules

 

 

 

 

Sorry, yes you're right. Finger trouble entering 0.25 (put 0.5 by mistake!)

 

What cylinder is in there?

[JinxDuh]

3 minutes ago, Lozart said:

 

 

Sorry, yes you're right. Finger trouble entering 0.25 (put 0.5 by mistake!)

 

What cylinder is in there?

Gearbox is completely Lct standard from what I can tell, the only thing I’ve changed is the short nozzle for a longer AK version - And the titan of course. The original shorter nozzle had no compression behind it at all, I took the o-ring from it today and it’s seen better days for sure.