[1tonne]

What the long range barrel does is it creates a little backspin on the bb so you do not need as much hopup and it also means the bb should be exiting the barrel in the exact spot each time.
In saying this I don't bother to use a LRB anymore. I use 6.01mm (or smaller) tight bore barrels and there is not much excess space. So the bb should exit in the same spot each time (or close enough). So, I would not bother. It can make your system fiddly.
If you do the LRB mod, test it first with no hop and see if the LRB can create some hop for you. It will not be able to create enough but if it can create a little then you should not need so much downforce from your nub.

 

[Marco]

I tested where the noise comes out of my gun, by covering half of it with a cushion. There is nearly no sound coming out of the muzzle and most of it out of the back end (cylinder/piston). To adress this area I can think of three possibilities:
installing a sorbo pad (currently the rubber cup of the stalker piston hits the metal of the cylinder head)
making the airbrake longer (it is a screw, that can be adjusted in and out)
making the airbrake wider (currently 4mm wide and the nozzle is 5,5mm wide)

can anyone recommend me which of the methods will do best or if thre is anything else to do?

All other methods (filling the stock, cylinder to barrel ration, long inner barrel, heavy BBs, grease on springs, 100% airseal) are done already. System is currently running at 3 Joules, 0,48g BBs, 435mm barrel and 9mm spring and springguide.

 

[SiliconeSword]

I have had very good luck putting a slightly oversized/tight O-ring in the cylinder between the cylinder head and piston, which makes more of a thud than a slap.

May or may not work with a cup style piston, but I'd give that a crack.

Other than that, make something like one of these or bury your gun in leaves and stuff

 

[E-11]

Hi, my experience with 4.2 mm sorbo 60°: won't help much even with a conventional aluminium piston. So I would not suggest that. Maybe a little rubber between hu unit and cylinder head would be another option.

 

[1tonne]

A short rubber between the CH and the HU does work but it then means the air nozzle may not go all the way into the bucking.

 

[Crius]

What helped me the most with noise reduction are these, in importance order:
1) Homemade "sorbo" pad.
2) Paper sleeve inside the piston.
3) Electrical tape on the top end of spring (side of spring that tangent with the piston)
3) Homemade working silencer.

 

[Marco]

What helped me the most with noise reduction are these, in importance order:
1) Homemade "sorbo" pad.
2) Paper sleeve inside the piston.
3) Electrical tape on the top end of spring (side of spring that tangent with the piston)
3) Homemade working silencer.

Could you explain your Homemade Sorbopad (I only have one from Laylax, whick seems to work well) and the Paper Sleeve? I think some paper inside the piston will get wrecked when cocking the gun, wont it?

Are you using an airbrake? If not is there a reason for that?

 

[SiliconeSword]

The paper is supposed to reduce the inner diameter of the piston reducing spring rattle.
This is commonly done with aluminum can(I prefer just making my pistons to fit a specific spring perfectly) but paper does the same thing.
I'm definitely curious about how well it holds up though.

As for air brakes, they reduce power and need a stronger spring to bump the power back up, which for some people that's an issue, or their piston would need irreversible modification to use one.

 

[1tonne]

What helped me the most with noise reduction are these, in importance order:
1) Homemade "sorbo" pad.
2) Paper sleeve inside the piston.
3) Electrical tape on the top end of spring (side of spring that tangent with the piston)
3) Homemade working silencer.

Different springs will make different twang noises. I have found Laylax to be about the best for noise reduction. So very little twang.

 

[Crius]

@Marco
My sorbopad is made from a common yellow thick rubber band, glued on cylinder head. I don't remember rubber's band thickness & don't know rubber's hardness. For sure is very soft.

You are correct. I should write <<thin cardboard>>, not just paper. A paper sleeve most likely will get wrecked. That's why I thought the cardboard, as it is stronger. I also chose the cardboard (not a metal can sleeve) as I wanted a metal part(spring) come in touch with a non metal part (hard paper). But you must be sure to fit well, and allows free spring movement. The cardboard is in use a year now without problems. It is just dirty...
I use the Airbrake that is installed on Laylax's piston.

@SiliconeSword
You are right about sleeve's inner diameter. The sleeve reduces piston's inner diameter, consequently reduces the room that the spring can swing inside and the lose of produced spring's energy. And when the spring swings, then it will hit the cardboard, producing minimum noise.

 

[Marco]

I think I should try the foam on the backend of the Hop up unit first. This area hasnt seen any modification jet, while every part else got modified a lot. I think a Sorbopad should do well there. I have the choice between the hard 1mm sorbo and the soft 4mm sorbo. I think the harder and thinner should do well. That way the nozzle isnt set to far back, also it wont push the nozzle back after coking the rifle.

I dont think there is empty space inside my piston for spring rattle, but I will check today. There is definitely no empty space between spring guide and spring.

The electrrical tape on the front end of the spring sounds good, I will do this today aswell.

Silencer is already done, there is nearly no noise leaving the muzzle of the gun.

 

[Crius]

I have the choice between the hard 1mm sorbo and the soft 4mm sorbo.

test both

 

[Marco]

ok, lets see what happens

some time ago I wrapped my gun in 3 layers of tape, following the stip the sniper guide for a silent vsr. do you think these layers of tape help keeping the noise in the gun or not?

 

[SiliconeSword]

Most definitely it helps, but only on the receiver really, as that's where all the mechanical noise is

 

[Marco]

I installed the 1mm sorbo now on back of the hop up unit. It reduced the sound by a noticable amount, thanks for the advice.

Now I have around 4 FPS Variations in my gun, before that it was 1-2 FPS. I achieved a perfect airseal on the front end of the inner barrel, so I dont see where this might be coming from. Any ideas? The stalker scorpion piston is slightly lubed inside the laylax cylinder.

Next will be the wider airbrake and the electrical tape on the end of the spring.

The sleeve inside the piston didnt work, because there is barely any empty space. Some thick grease on spring guide and spring should do the job (I wasnt hearing any twang while testing).

 

[SiliconeSword]

The squish factor of the sorbo is undoubtedly making the nozzle go in slightly different depths, slightly changing air volume, but more importantly BB position on the contact patch and nub.
+-4 is still alright, but you'll just have to decide if there's an accuracy change and if it's worth the sound improvement.

I tried the electrical tape thing and it worked quite well, definitely will help a bit, along with some thick grease like you say.
Still, nothing compares to making a wooden box lined with aluminum foil and carpet covering the whole gun.

 

[mrFonzie]

Action Army Cylinder Dimensions
Piston Travel Length: 90.2mm
Cylinder diameter: 22.5mm
Compression Volume: 35864 mm^3

So see the chart below:
0.3gm bb use a 554mm barrel (15821 mm^3) = 2.26:1
0.32gm bb use a 530mm barrel (15136 mm^3) = 2.36:1
0.36gm bb use a 500mm barrel (14279 mm^3) = 2.51:1
0.4gm bb use a 470mm barrel (13422 mm^3) = 2.67:1
0.43gm bb use a 430mm barrel (12279 mm^3) = 2.92:1
0.45gm bb use a 400mm Barrel (11423 mm^3) = 3.13:1

Just a question:for the right measurement of the ratio rapport between barrel and cylinder, should I consider as volume of the cylinder the space around the airbrake or not?

 

[1tonne]

No. You measure the area between the tip of the air brake and the cylinder head.
The air that is caught because of the air brake can no longer be part of the cylinder volume as it then becomes part of the air cushion volume.

 

[SiliconeSword]

I'd suggest that you measure excluding the air brake, and then subtract 50%-70% of the length of the air brake.
This should get you more on the line of what you need as the air brake will need to go into the nozzle a bit before it kicks in.