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Expanding foam

8791 Views 21 Replies 12 Participants Last post by  sanguinor
I was pondering on different methods of silencing my G&G M14 and was wondering if expanding foam could be used to fill certain areas of the stock around the gearbox as there is a couple of dozen little holes there. As it says in the description of the Polycell stuff; "it shoots liquid foam deep into cavities, creating a long lasting seal, which insulates against heat, sound and moisture"

I could then file down the foam so it would fit the gearbox correctly/snugly. I could even apply this to the rear of the stock to fill out where I put my battery (to stop it from rattling around and reduce the boxy noise of a hollow stock) and the front end of the gun (as there are holes in the front sections which could be causing noise) if any benefit could be gained from it.

As a further thought, could it also be used to secure my barrel once my LRB is correctly set up, but then would it stop me from removing the barrel afterwards? Could the barrel be coated in a 'non-stick' coating such as Vaseline, silicone grease or another lubricant to prevent the foam from adhering to it?

Thoughts?
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I filled a BAR10 stock with the stuff, and it is very, very messy and sticky. If I were you I'd buy some foam board insulation and cut and file that to fit between the gearbox and the stock.
People commonly use it to fill VSR stocks. I have some in a bag so that I can test claims that filling the stock improve accuracy a measurable amount. Need a garden so I can do the testing though so I have not yet used it.

Solid foam cut to shape is more commonly used for actual sound damping though.
There is another foam, and I can not remember the name of it. I have seen it used for costuming, and it dries firm and rubbery (sure it is actually rubber). A good art store might be able to give more direction, It might do better than insulation foam.
Go to a craft store and get come craft foam.

Spray foam is nice, but if you do it wrong you are going to make a sticky nasty mess of the rifle.
You could always use dynamat. Vindi shows how he did it in his DMR thread.
You could take the beadboard styrofoam you get with a lot of large packages to hold the thing in place, like a microwave or something, and shove that in the stock. If that doesn't help with the noise you could also use the packing peanuts found in packages. If you really want to go the extra mile get that noise canceling foam they use in music studios. I used non-hardening modeling clay in every nook and crevice that has open space and brought it up to a realistic weight while quieting it.
You could use the expandable foam, but use liberal amounts of vasaline as a release agent on anything that may come in contact with it that you dont want it to stick to. Then sand/cut down the excess.
I already have a lot of my stock filled with packing foam so the reason for me asking this question is simply a "How can I make my gun quieter?" It's already quiet, but I think it can be better. This is the reason my friends know my guns going to break, I'm always trying out new things so I can I can get that little bit more performance by doing another tiny tweak or change.

I will have a think about what you guys have said and then give it a blast, the modeling clay sounds like it'd be good for around the gearbox.
You could try a similar method to real steel gun bedding :shrug:


I've just done my VSR scout and it made a bit of difference to both accuracy and sound as it holds everything rock solid.

I used 2 pack body filler, mixed it with half the recomended amount of hardener applyed it in small amount to the stock then, after sealing with tape and covering in grease and cling film, pressed the mechanics into the stock and firmly clamped them together so that the filler squeezed into any voids.

Keep a small amount of filler on your mixing board so you can guage how hard it is, and when its just starting to cure hard pull the mech box out, then re-insert it, then take it out again..... and repeat a couple more times until the filler is hard.

What you should have is a solidly mounted gearbox that has all the tracks gouged out to allow it to be removed easily.

You may find it needs repeating a couple of times to get all the spaces filled, and its always better to do alittle at a time as this makes mistakes easier to cure :yup:
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If I followed that correctly Vindi, the plan is too slap filler into the places I want filling then place my gearbox (protected with clingfilm which is coated in grease to prevent sticking) into the stock so the filler can take the shape of the gearbox as well as the stock.

Then, when the filler begins to dry remove the gearbox and re-insert it. Repeat several times to ensure that the filler has molded the tracks needed for insertion and removal of the gearbox?
If I followed that correctly Vindi, the plan is too slap filler into the places I want filling then place my gearbox (protected with clingfilm which is coated in grease to prevent sticking) into the stock so the filler can take the shape of the gearbox as well as the stock.

Then, when the filler begins to dry remove the gearbox and re-insert it. Repeat several times to ensure that the filler has molded the tracks needed for insertion and removal of the gearbox?
Correct :tup:

It can be abit messy, though no where near that of expanding foam, and once hard can easily be carved/sanded to fit.

Like I said, I've just done it to my VSR scout and the results are positive, but as I was only messing with a trigger group it was quite easy, I'm not sure how it would fair with all the moving parts etc that are involved with an AEG, but I'm sure if you were carefull with how you protected them to enable them to still function properly it'd still be perfectly feasable :yup:
Vaseline and cling film... Liberal amounts plus liberal amounts of in and out afterwards... I feel sorry for people who haven't taken the time to read this properly and have skimmed to the bottom!

Still, I will be using the spare gearbox for this one. Just in case.

What do you think to using the expanding foam to fill the outer barrel though? To give it the stabilization?
Just a thought, I was reading somewhere about Airsoft G.I. doing an upgrade on a rifle where they used a "rubberized paint" which aided in the handling/grip of a rifle. Would rubberized paint not help deaden at least some of the internal noise? Also I am assuming you are using this in a sniper role, if so, can you thicken your rifle's ghillie "sock" or wrap? It's just me but I'd be worried about putting something expandable inside the rifle, then again, I am new to the sport.
I understand where you're coming from there Jute, the expandable foam is something that'd be done a bit at a time under controlled conditions. There's no way I'd just dump a load of that stuff in and watch it take over my rifle like a weed in an untended garden.

Rubberized paint ey? I've not heard of that, that's something I will have to look into!

I hadn't thought of the sound deadening effects that the Ghillie sock could have... It'd be quite easy to slide a wrap of foam around a good portion of the body underneath the sock. I will have to give this a try at some point :)

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Rubberized paint ey? I've not heard of that, that's something I will have to look into!
Yup, I painted someones bathroom floor in it on wednesday!!

I'll stick to wrapping my barrel in Etape to about 5mm thick for the time being, less messy, slightly more effective :yup:
Electrical tape no?
Thats Correct :tup:

I do it in bands side by side leaving about 3mm gap between them, I also make the Etape external diameter totaly variable, between 3 and 5mm, you can go bigger than 5mm if you have the space inside the outer barrel, this disturbs and breaks up the viabrations harmonics, its almost as good as any solid barrel spacer :yup:
If you Google "plasti dip rifle stock" or simply go to http://www.plastidip.com/home_solutions/Plasti_Dip you should see the product. They now actually have specific camouflage colors as well. I honestly think that between a coat of this (which can be removed should you want to sell the rifle) and the ghillie sock and wrap on the exterior of your rifle should provide serious sound deadening. A Google search will return photos and videos of rubberized stocks in addition to articles. Best of luck!
Ive used expanding foam in my m14 to fill the stock before and it worked great.I dont really get why everyone says it wont work.But then again im just going off my own experience.Mattress foam and packing foam work well also.
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