Getting an AUG quiet.

[Iceni]

I've been playing about with my gun a bit in an attempt to make it quiet. Currently it is loud on your ear when shooting, but when been shot at you can hear a little motor whine and a very dull thud of the piston. Outside of about 10 meters it's pretty much silent, I can even get away with dry firing in the house without the wife noticing.

I think I'm almost there but was wondering if you guys could look over the list of modifications and see if there was anything else I could do.

V3 box,
New loom, 3034 fet, Silver wire, Deans.
Shimmed, SS bushings, M100, Solid brass guide,  POM piston and cylinder head.
Nylon stock piston metal front tooth type. 5g extra weight.
SHS high speed, shimmed.
Stock JG gears. SHS air o-ring air nozzle.

CNC hop, 50deg lonex flat hopped, 6.03 509mm barrel.

120mm silencer (foam spring type).
Some foam packing on all inner panels (4mm floor matting) There is more space I can fill.

Magwell foam lined, Metal front plate (homemade) (solid mag seating no wobble).

I'm seriously considering filling the remaining voids with loose fill fireproof insulation.

And I'm thinking about a second blanking cap for the brass eject.  And removing to top baffles to allow a better lump of filler into that space.

There is also space on the upper for a foam plate to seal the front side of the box.

ATM it's shooting at 340FPS, At 25RPS, on a 7.4v 30c.

Am I scraping the barrel trying to get more from it. The reason for all the upgrade is I'm going to do a DMR AUG as my next gun. So this one is the test bed.
 

[Hangtight]

Best way to lessen the motor and gear whine is to move to a 16TPA motor, 13:1 gears and 7.4v. The lower pinion speed along with correct pinion /bevel mesh will help.

A shorter barrel will be needed for a DMR as you'll never get decent efficiency from the available air volume when using heavier BBs. Heavier BBs can also slightly reduce the piston velocity which lasts the 'thump'.

But if you've got it to the point where it's inaudible outside your MED then there's not much point doing more.

[Lozart]

The biggest issue you face (as with all bullpups) is that the gearbox is right by your ear.

 

Instead of packing foam I would suggest something like Dynamat (for car audio installs) although you might find it a bit tricky to install without splitting the shell in half (it's adhesive backed). Plus it's bloody heavy in any great quantity.

[Iceni]

6 hours ago, Hangtight said:

16TPA motor, 13:1 gears and 7.4v. The lower pinion speed along with correct pinion /bevel mesh will help.

That actually might be a plan, I have a decent neo shell kicking about so I might see about picking up a 16TPA inner for it. I might already have one I do have a habit of picking up motors when I go shooting if players have them for sale. I have a couple of different models sat about so I'll have a turns count on them.

As for the gears I was thinking about an helical set at some point. They should have better efficiency, And that would reduce noise and heat losses. I kept the JG ones simply for the fact they appear to have been correctly hardened, After 3 years of owning the gun they show no signs of wear.

 

I am running a high grade moly grease designed for model train gearboxes. It seems to do a better job than the regular grease I was buying. It is really nice and thin, but also very sticky. And doesn't seem to smash out like the regular stuff does.

 

6 hours ago, Hangtight said:

A shorter barrel will be needed for a DMR as you'll never get decent efficiency from the available air volume when using heavier BBs

I need to research all of this before I move forward with the AUG DMR build. I should have a decent understanding of the platform and gearbox by the time I move onto the build, but knowing what base model to pick up will be a part of the process. All I know ATM is it will be a 400-450fps semi only build. The research that goes into the build before I even start will be as in depth as possible, It's one thing I am good at.

The reason to stick with the AUG platform is it works. I don't have the same restrictions an M4 platform imposes. I have better motor engagement, Wire space, and a stronger base shell. As well as having the room to make the aug quiet. Other guns don't let you do so much so easily. I also have the correct compliment of mags and batteries for the platform.
 

 

1 hour ago, Lozart said:

The biggest issue you face (as with all bullpups) is that the gearbox is right by your ear.

 

Instead of packing foam I would suggest something like Dynamat (for car audio installs) although you might find it a bit tricky to install without splitting the shell in half (it's adhesive backed). Plus it's bloody heavy in any great quantity.

Yup right by your ear, And I haven't packed out the top of the box at all yet. It just has a 4mm skin over the sides. If I take out the upper baffles and add a second rubber cover then I should be able to make a pad that sits in the correct place over the top of the box. And will still allow access to the hop. 

Weight on the rear of the gun won't be a problem, It's currently balanced right on the pistol grip and is fatiguing on the shooting hand. A little more rear weight should move some of that weight onto the shoulder and that's not a bad thing. It is one of the older ASG A3's so the other option has always been to cut the RIS for the same effect. The shell itself won't split, I've already tried and the glue they have used has bonded well I'd be worried about breaking plastic. It doesn't mean I can't make a brass plate with the sound deadening glued to that that slips in with the gearbox, Without the baffles there is space over the box for exactly this style of remove-able sound damping. If done right it should work.
 

[Rogerborg]

12 hours ago, Iceni said:

Nylon stock piston metal front tooth type. 5g extra weight.

 

Apologies for the noob question, but why add weight to the piston?

[Iceni]

The weight in my case was shaped to hold the spring. It's an original part from the gearbox. The new POM piston head didn't come with one but I put it back in because without it I was getting a fair bit of twang noise out of the spring. The weight seems to stop a lot of that noise and you really hear it with with the AUG.

Other than that I haven't seen any significant performance gains for having it. And the front of the V3 box is strong enough that the extra weight shouldn't cause any significant problems like cracking.

It's a slightly larger lump than the one that comes with this head. Big enough that the spring is held by it.

[Hangtight]

4 hours ago, Rogerborg said:

 

Apologies for the noob question, but why add weight to the piston?

 

If you're looking for maximum efficiency when firing heavy BBs then a heavier piston is more effective than a lighter one, and may even allow you to use a lighter spring. But it's not a good idea in a full auto gun as the increased piston weight slows the cycle time, possibly to the point where the piston hasn't finished its stroke before the sector gear comes around again. It's wasted with lighter BBs and will give the gearbox a harder time.

[Iceni]

1 hour ago, Hangtight said:

But it's not a good idea in a full auto gun as the increased piston weight slows the cycle time, possibly to the point where the piston hasn't finished its stroke before the sector gear comes around again.

Last internal inspection of my box  I made a point of checking my piston teeth. It was build using the stock one to add a point of failure, I'd rather chew up a piston than chew the gears.

As it stands there is no noticeable wear on the teeth. I'm in no doubt that if I went crazy with gear ratio's and motors then this wouldn't be the case. 25RPS with 110 and 170 rnd mid caps is plenty fast enough. I'd much rather have money invested in the hop and airseal, And have good reliable BB trajectory and consistent aim than be able to spray a full mid cap in 2 seconds. ATM I think there is room for improvement but that is more the shape of the nub I'm making rather than the setup. Currently I'm using a flat nub made from hard blue ink rubbers. I will at some point produce a series of nubs and test a range of shapes and see what one works best with my hop.

 

There are a few weighting systems if you wanted to play about but I can't recommend them. Most of the kits are power tune spacers to get up to the fps limit and are made pretty lightweight, but some companies do weighted/metal spacers to add both mass and spring compression. The type I have just adds weight and removes spring slap.

https://www.powair6.com/en/piston/4997-orga-power-adjuster-aeg-spring-spacers.html

https://www.powair6.com/en/piston/5399-balystik-power-adjuster-aeg-spring-spacers.html

[Hangtight]

Get yourself some 70 durometer urethane sheet for nubs. I used to use the hard blue eraser, but the urethane is better.

ICS orange pistons are good for reducing spring 'twang' as they're a really good fit to the spring diameter. You can also put a hard nylon sleeve on the spring guide to match the ID of the spring. After that you're onto using some of the spring 'tar' greases sometimes used in spring air rifles to damp vibration in the spring, but these slow the cycle time too much.

Increasing piston weight is easy. You can simply take the bearing off the guide and add it to to the one already inside the piston, or use washers of the same thickness so you maintain the spring compression.

The kits are way overpriced. You can find hardware that'll do the same job, sometimes better for pence.