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Discussion Starter · #1 ·
Hi guys, new user here.


I have recently built a new VSR rifle using a cyma 701.b.


Due to the recent lockdown I haven't been able to test it fully, but from firing it (safely!!) indoors, there seems to be a very loud noise. I have filled the stock with foam, but any other tips would be greatly appreciated.


The parts I have used are:
Action Army Twisted Outer Barrel (Long version/430mm)
Action Army CNC Upper Receiver
Action Army Zero Trigger
Action Army Twisted Cylinder
Action Army Hop Up Chamber
Maple Leaf 430mm Crazy Jet Inner Barrel
Maple Leaf 70 degree MR Hop
Maple Leaf Omega Nub
Wasp Piston (Heavy Weight/Medium Air Brake)
Wasp Spring Guide

Rapax 2 Joule Spring
Sorbo Pads


Thanks guys!!
 

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Also, what is your bb weight that you are shooting.
Do you have a silencer? They also can work a treat if done correctly
 

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Discussion Starter · #5 ·
Currently using 0.4's, although this may change when I get back out to the field.

I haven't tried a silencer because I don't really want to make the gun much longer than it already is. Although if that's what's needed, can't hurt to try

Sent from my SM-G977B using Tapatalk
 

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You will be getting a little bit of excess noise out of the barrel because the barrel is a little short for 0.4gm bb's. I would try a 470mm inner barrel with a silencer.
 

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Or use a heavier bb weight. With a 2 joule spring many people use .45g+.

The heavier bb will use more air in the barrel before it comes out and result in a quieter sound as well.

Keep in mind most of the sound is coming from the piston, not the barrel end, but heavier bbs and a suppressor will help some. Adding foam was a good first step as it reduces vibration noise in the stock. An airbrake or sorbo pad on the piston could be considered.

Using a piston with a cup style head instead of an O-ring will also give you a quieter rifle.
 

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I was thinking of suggesting a heavier bb but at only 2 joules I was a little unsure. I know that at 1.9 joules, a 0.4gm bb works really well. But heavier bb's may also work. I would suggest a 0.43gm. This is the correct ratio for a 430mm long inner barrel.
 

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RAPAX 2J is the typical spring choice in the UK. It'll produce the UK limit 2.3-2.5 joules with the right barrel length, piston, and bb weight. Pretty sure Kicking Mustang still uses .48g at that power level as well.

That's the only reason I suggested the increased weight.
 

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Discussion Starter · #11 ·
Cheers for the tips guys, ordered some heavier bb's and cotton wool :)

Would you recommend using the "full" airbrake that comes with the wasp piston?

Sent from my SM-G977B using Tapatalk
 

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Using the full airbrake with the WASP will depend on the spring you have. With a RAPAX I wouldn't recommend it as RAPAX are long springs. This means the brake will have a dramatic effect on fps loss and likely won't quiet the gun much.

I'm using the long airbrake that I dremeled down to ~2/3 length and tapered the end of. It quiets it... some, but also doesn't effect my fps as much at that length with the taper. The main advantage of the WASP in the VSR (for sound) will be the cup style head that dampens the noise.
 

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Can't understand the need for an air brake. Every high end VSR that I have built has been as quiet as a Socom pistol. The only time I could see an air brake being a good idea is if my inner barrel was too short or I did not have a silencer.


Also, one other thing to note: I make my own foam to go inside a silencer. I use foam from an old crappy mattress (very soft and bouncy). Just push the silencer onto the foam and twist sideways until the foam it cut into the silencer. I then use a 8mm hole punch to cut a hole in the middle of it.
When putting the foam back into the silencer, you will notice that the foam compacts a little and this makes the central hole a little smaller. So the hole is only about 7mm in diameter. Just enough for the bb to get through. This works a treat.


But even if I use standard foam inserts, my rifles are quiet.
 

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Can you describe the noise? Is a hard thumping sound?
Or is it the clanging spring sound?
I can’t remember the sizes, but I do remember there were different spring diameters, lalax had a smaller diameter using a smaller spring guide that would rattle on firing...
The next size up used a larger diameter spring..if I remember correctly The 1 I’m using was meant for an aps. Easier pull, and smoother sounding
 

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Do you have the end cap on? That dampens the sound a lot
 

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Discussion Starter · #17 ·
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