A silent, suppressed GBB

[Dimitri MdP]

(ported from my previous post at ASF)
 

Well kind of a weird, accidental finding kicked off this project; 

 

I was playing around with Poseidon's Ice Breaker piston head for WE GBB pistols, a gimmicky thing with 2 teflon rings instead of the typical oring / seal cup, which is supposed to "improve cold weather performance allowing less gas consumption and more shoots". 

 

 

Spoiler alert: it certainly does not. It didn't even provide a seal at all, until I opened the clam shell design and put some teflon tape bellow the rings in order to expand them. 

 

After quite some test to adjust the diameter in such way that it provided a good seal while not getting the nozzle stuck, I found something extremely weird: it muffled the sound.

Not just a "I think it sounds somewhat quieter", but a complete modification of the sound signature: the highs and mids get totally cut off. leaving only a bassy "plop" behind, and the perceived volume is about a third of the regular sound or even less. 

 

 

Kind of makes sense since the sound of a GBB doesn't come from the barrel as it would in a real gun, but is mostly piston pop + metal clings from the working parts. I'm not sure how the Poseidon piston head modifies the piston pop in such a dramatic way, but it certainly does.

 

In the particular case of my WE makarov the slide noise is already taken care of by a tiny pad /buffer above the trigger guard, and it also includes a suppressor which I'm gonna foam fill (legal down here) just to see if it further lowers the perceived volume. 

 

 

 

So there's that. I'll make sure to get some proper DB readings, practical field testing on "how far can you hear that", and maybe some recordings to compare the sound signature.

 

I might have (accidentally) found the way to achieve a somewhat silent, sniper-worthy pistol without the awful dead feeling of NBBs. 

 

If all of this goes as planned, I might even go into the hassle of turning it into a proper PB to go along with my Russian Army SVD loadout

[Gunnman]

I would like to see a DB comparison. You could probably get an DB meter app on your phone.

[renegadecow]

You do still get a good pop out the barrel but is mostly for short guns. The KWA MP9 for example is horribly loud.

As for piston pop, it looks like the Ice Breaker is able to bleed out some gas through the nylon ring. If that's the case, pressure isn't built up as high on a stock cup so the resulting decompression (pop) when it clears the nozzle wouldn't be as strong/loud.

I've only experimented on putting o-rings as buffers on an WE AR bolt (front and back) which greatly reduced the metal-metal sounds. I'm thinking maybe a spring loaded piston cup which will dampen the last few mm of the slide returning to battery should work for pistols. 

[Dimitri MdP]

As for piston pop, it looks like the Ice Breaker is able to bleed out some gas through the nylon ring.

Well, it uses 2 rings, with the aperture in opposed directions.  But I think you're still somewhat right about that.

 

WE Makarov's original suppressor has an internal tube to keep the inner centred and prevent baffle strikes, but I'll find the way to do without, so I can foam fill it. It's definitely not the most efficient gun with that short, short barrel, so maybe it will actually further decrease the noise produced by over volume.

 

As for the slide noise, it's not a particularly noise gun in that aspect, I would dare to say it's actually one of the quieter I've seen to begin with. But I'll see if I can find the way to install some thin rubber pad without getting the slide out of battery

 

 

I would like to see a DB comparison. You could probably get an DB meter app on your phone.

Will do. But phone mics have integrated compression, so they are not good for this sort of thing, and DB meter apps can be calibrated all over the place.

 I'll make sure to take some "professional" recordings next weekend. 

[Gunnman]

True, I downloaded a couple of DB meter app, and found it be hard to accuratley calibrate.

[ninja master of coffee]

I guess the main issue you'd run into with a PB is relocating the recoil spring since the real thing has it located in the back strap and is actuated by a lever... Still, another issue for another day I guess?

[Dimitri MdP]

I guess the main issue you'd run into with a PB is relocating the recoil spring since the real thing has it located in the back strap and is actuated by a lever... Still, another issue for another day I guess?

yup, first gotta check if the reduced sound signature on the regular WE PMM(ish) with the suppressor is enough, then try the conversion just for aesthetics / reenactment purposes.

 

I've been already working in that idea for some time and got the right springs and a halfway done design for 3D printing the correct grip to accommodate that. The gun has a ridge inside the slide, on the right side, which normally is used to lock the BBU but can probably be moded to operate the recoil lever as well. So that makes it a feasible project.

[renegadecow]

Personally I wouldn't bother making the recoil spring realistic since it's already got an unrealistic double stack mag plus it's in the way or you'll have to fatten the grip significantly. Instead I'd leave the slide to operate as usual, build up the sides and have the cylinder portion only as a shroud attached to a 14mm thread adapter.

[Dimitri MdP]

I don't really understand your idea there...

[renegadecow]

-put on 14mm thread adapter

-cylinder shroud around the barrel attaches to adapter (by grub screws or whatever means) and only covers the front of the slide i.e. hollow

-attach custom suppressor

-add cosmetic material on the frame and slide for beefed up portions

 

This will make for a relatively easy conversion as all of the original mechanisms of the slide is intact. It will of course give itself away if the slide is locked back as it will reveal the part of the slide hiding under the cylinder area.

[Dimitri MdP]

well that might work... but I still have to 3d print the correct kind of grips, so I might as well try the PB recoil type, before cutting anything on the slide itself.

[3vi1-D4n]

I managed to get an MP9 to drop from 80db to 68db @ 1m away shooting at a foam target (no impact noise), using an angry gun silencer with powerup barrel removed, and added felt baffles.  Without battles there was no drop in db, except for the tone of the noise.  Current temperature is 20*C, FPS at 390fps.

 

The MP9 is a great platform for silencing as it has a massive sorbo pad at the rear end of the receiver, as well as a plastic outer barrel that effectively absorbs the impact from the bolt.  The only downside is that by default is a noisy GBB (short barrel, conical outer barrel crown, with barrel sleeve serving as a loudener)

 

Ironically that is as quiet as as airbraked G&G MP5SD6 I created, dropped from 75db to 68db, though the power is a fair bit lower since the airbrake takes away the air to use for braking.

[renegadecow]

Being encased in tupperware also helps.

[Dimitri MdP]

I managed to get an MP9 to drop from 80db to 68db @ 1m away shooting at a foam target (no impact noise), using an angry gun silencer with powerup barrel removed, and added felt baffles.  

 

Will try the baffles thingy. Thanks for the input.

 

Being encased in tupperware also helps.

And shooting underwater might do the trick too. Still, not really practical, is it?  

[renegadecow]

And shooting underwater might do the trick too. Still, not really practical, is it?

 

Referring to the MP9's plastic clad exterior.

[3vi1-D4n]

Referring to the MP9's plastic clad exterior.

 

At first it did sound like sarcasm, but I understood it in the end.

 

The baffles are basically spacer/pads for furniture so as to not scratch wood floors. I bought at the bargain stores for $2 for 8 pads.  I drilled a hole in the middle and then blow torched it to enlarge the hole to the appropriate size.

 

In the past I also used hair gel in the silencers in between baffles, but found they dried up too quickly.  Petroleum jelly may do the trick.