How to quiet the big guns for indoor shooting

by B.B. Pelletier

I wrote this last year, but didn’t publish it because there was some question about whether this constitutes a silencer. I don’t believe that it is, according to the intent of the law. Dr. G. asked me yesterday about how to quiet powerful airguns for shooting in the home, and I thought about this report. So, today, I’m publishing it.

This one’s for Anatoly, who asked about installing a shroud on his AR-6. It seems he’d like to shoot his rifle indoors. He’s not alone. Many shooters have a powerful hunting air rifle they would like to shoot indoors. That’s no problem as far as safety is concerned. Get a heavy-duty metal bullet trap designed for .22 rimfire and no smallbore airgun in the world will overpower it. But the noise these guns can generate is another matter.

I told Anatoly that it’s possible to install a shroud on his rifle, but the fact that he was asking probably meant it wasn’t a project for him. There’s a lot of machining needed to shroud an AR-6. If you don’t have the tools or the inclination, it’s not a job to undertake. But that doesn’t mean you can’t enjoy a quiet gun indoors.

This trick is older than me and it’s perfect for loud pneumatic and CO2 guns. It isn’t as effective on spring guns because most of the noise they make is produced in the powerplant, where this solution has no effect. What is it? Nothing more than a simple cardboard box lined with sound-deadening material.

The portable silencer
The box has two holes cut in opposite ends. To be effective, it should be at least 18 inches long, but 24 inches would be better. It doesn’t have to be a big box. The sound-deadening material can be any soft material, but pink fiberglass insulation is probably the best. This goes on all surfaces inside the box and can be held in place with staples or tape.

The box works by sticking the muzzle of the rifle inside at least one-third of the way. With experimentation, you’ll discover how far is best. The holes have to be large enough so the sights or scope can see the target unobstructed. And the box needs a stand so it can be positioned.


The quiet box is simple to make from a cardboard box. It will reduce the report of your more powerful smallbore air rifles so they can be discharged indoors without disturbing the family.

Even though there’s a large opening on the muzzle end of the box, the sound of the gun will be cut significantly. I call a 4-inch wide by 6-inch high opening a large one. That gives you plenty of room to aim the rifle but still traps most of the major sound waves. Those it doesn’t trap get broken up. What escapes the box sounds much quieter in comparison. It must be obvious that an adjustable stand for the box is going to be essential, and that’s up to you to make or find. It doesn’t have to be that difficult. If you’re a non-handy man like me and Red Green, you can bungee the box to a tall pole that has a firm base–like a light stand, for instance. Not elegant, perhaps, but entirely functional and adjustable.

Works for big bores, too!
I remember telling big-bore maker Gary Barnes about this trick and I’ll darned if he didn’t build one for his shop. He calls it his “ballistic mailbox,” and it’s made of steel with fiberglass insulation inside. With it, he can test 500 foot-pound airguns in his shop, which is located in town. Though he used metal, you don’t need that kind of strength for a smallbore that’s only producing 80 foot-pounds or less.

Don’t like fiberglass?
You can use things other than fiberglass insulation to line the inside of the box. Other types of insulation would be a second choice, but even soft carpet will muffle the sound more than you think. Shag would be better than a Berber weave. What you’re making is a variation of an acoustic anechoic chamber, which is a chamber that absorbs sound waves and doesn’t reflect them back. The opening in the muzzle end of the box also disrupts the discharge sound waves and doesn’t allow them to leave the box with the same strength they left the muzzle.

Give this project a try if noise is a problem in your house. Be sure to tell us the results!

50 thoughts on “How to quiet the big guns for indoor shooting

  1. WOW it sure is quiet here this morning…Maybe everyone is making a wife happy box.just to be different I’m going to use eggcrate foam and see how it works.thanks for reminding us of this great little helper! FrankB


  2. The other major component of sound from shooting is when the pellet hits the trap. This sound can be reduced, too, buy putting your trap inside a similar box. I had a Gehmann trap that was pretty quiet but I reduced its noise considerably by putting some fiberglass batting behind its plate.

    Finally, some sound-proofing material on the ceiling of where you shoot will also help. Of course, the ultimate sound trap would be a tunnel lined with batting or similar material.

    Best,

    Joe





  3. Also, since one of the best sound dampeners is air space, if you could put your new box inside another larger box, with no parts of the two boxes touching each other, the sound would be dampened even more. You’d have to experiment to get the most practical separation. I read about air space as a dampener while looking to sound proof my condo from noisy neighbors. I didn’t do it, however, because it was more expensive than it was worth.

    Check this out:
    http://www.soundproofing101.com/soundproofing_3.htm

    -Chuck



  4. Another project – now that the RWS 350 is sorted, the gas cap on my Triumph motorcycle now vents and none of the cars or bikes need to have their oil changed or tires rotated and the wife hasn’t made a decision on what she wants the kitchen to look like, I can handle this! LOL.

    I’ll let the list know how it works – firing my Discovery scares the crap out of my cockatiels and annoys the wife.


  5. Sounds of silence.

    Neat idea.

    However, if I could be so bold. I would suggest substituting the fiberglass insulation with other building materials. First if you’ve ever handled a piece it can be less than pleasant. (At least get one with Kraft paper on one side.) Secondly, it is one of the least effective building materials for controlling sound. As a builder we often received requests to quiet a room, with the number one area being a bathroom. Potty shy people I guess. Typically these folks would just ask for the same R-13 that goes in the exterior walls. We then had to explain why this was a poor choice and go over the options.

    Research has shown Fiberglas insulation works for temperature well but sound poorly.

    There are bunches of sound deadening materials out there, but some of the ones made for autos may be the best for this application. (just google) Foam type with a backing or jute would keep the box light. If you want to keep the cost down acoustical ceiling tile could be a good alternative.

    Lastly, don’t over look using your whole house when shooting outdoors. I have removed one key screen from a window and this works well – just make sure the muzzle stays in the house.

    http://www.thisoldhouse.com/toh/article/0,,212626,00.html

    Volvo



  6. Vince,

    You CHALLENGE me?

    So CB Caps don’t cycle autoloaders, eh? Well, just because you are right doesn’t make IT right!

    I have an ongoing series of articles in Shotgun News called “What can you do with a 10/22?” I’ve done five parts so far, and it’s been over a year since the last one – maybe two years.

    So I accept your challenge, Mr. Vince Know-it-All. (The fact that you do proves nothing.)

    I will modify a 10/22 to function reliably with CB Caps. And I will have YOU to thank for it.

    The now-challenged B.B.


  7. MCA,

    A CB Cap (and also a BB Cap) is a .22 rimfire cartridge without powder. All it has is the priming compound. The case (for a CB Cap) is supposed to be as long as a long rifle case, so shooting the caps doesn’t ring (erode) the chamber of the rifle or pistol the way shooting shorts in a long rifle chamber does.

    BB Caps are hard to find these days, but they are nominally based on the .22 short case and have the same arrangement for power.

    Some CB Caps are much hotter than others. I like CCI caps and Eley Zimmer Patronen.

    A slow CB Cap should propel its 27-grain lead bullet around 650 f.p.s. – but that depends a lot on the length of the barrel.

    B.B.


  8. OK, Mr. “I can make an M1 Garand cycle with percussion caps”… ya gonna make it work with CB shorts, or ya gonna make me buy longs?

    Of course, I’ve got a 10/22 – so maybe I will have a go at it… hell, not knowing what I was doing never stopped me before…

    MCA – http://www.cci-ammunition.com/ballistics/rimfire.aspx

    …and scroll to the bottom of the list. Hit ‘Detail’ for the CB’s, and you’ll see that it is capable of propelling a 29gr bullet at 710fps, for a total of 32 ft-lbs of energy.

    Also note the energy retention – almost 88% at 50 yards. In contrast a Crosman Premier .22 pellet, launched at 714fps, retains only about 61% of its energy over that distance (according to straightshooters.com). Just an additional confirmation of BB’s point about the relative safety of the diablo pellet vs. a bullet…


  9. B.B.
    Sure could have used one of those box silencers a little while ago. My ears are ringing from shooting in the basement.

    Talon with Condor power plant,185 bar fill, pw5.8,th unknown, end pressure 140 bar, kodiaks, 32 shots….
    Prochrono says….
    936 939 930 935 941
    944 948 952 955 960
    965 953 956 956 956
    957 963 958 960 959
    951 957 954 951 952
    944 942 944 936 935
    932 930

    twotalon


  10. B.B. & All

    We've been swamped again, and I missed a couple days of the blog..

    Yesterday's blog was too hard for me to face!! I know you had my impulsive buying habits in mind!!
    You mean, I need a good reason to buy guns!! I'm in big trouble!!

    Asking myself hard questions before buying.. are you crazy? that makes too much sense for a "Wacky Wayne"…

    Today..

    The box seems like a practical idea..

    And don't forget about the "duct seal" type traps for the other part of the noise.. no noise at that point as well and no bouncing around.. like inside the metal traps.. I think you can stop whatever you want to, by just adding more thickness of the clay type material..

    Or.. just buy the right gun or guns to start with!! Air Arms s410.. quiet, very accurate, power when you want it, no boxes to mess with.. a "do it all" type air gun..

    Right Kevin?

    Wacky Wayne..


  11. Yeah, I think Volvo is right, plus breathing fiberglass is a really nasty thing to do. It doesn’t break down in your lungs. It stays there forever, so I’ve heard. How about some of that foam insulation you can spray into window frame cracks etc? Except if it hardens up it won’t absorb sound very well. Maybe that Styrofoam acoustic ceiling tile Vince mentioned, and it’s very light.
    -Chuck


  12. BB,
    I have a 10/22. How can I get at all your Shotgun news articles about it. I did a search there on “Gaylord” thinking they’d show up but instead got one bazillion other articles written by you. Whoa, you a busy man! Then, I did a search on “gaylord 10/22″ and got nothing. Then, I did a search on “10/22″ and got another bazillion hits. Where’s Waldo…I mean Gaylord.

    -Chuck


  13. As people have mentioned, I would think the noise from the impact of a high power pellet is at least as great as the sound of the discharge. Surrounding the target with another cardboard box might do it although I expect that you would have to seat your target well back from the entrance of the box. And if your opening is 4X6 inches that restricts the aiming and lighting on the target. Duct seal still seems to be the best solution.

    As for the cardboard box idea, let’s just say that it makes my life possible as I know it. However, the openings in mine are much larger, say twice the area of an 8X11 sheet of paper. I think what saves the day is that I have lined the box with a variety of things, sweatpants, seatshirts and small, empty cardboard boxes to absorb sound. Plus, I close the door and windows of the room. That seems to work. BUT, it raises another serious issue of indoor shooting–especially with high power–which is the presence of lead dust. I recall the blog saying that a pellet will fragment at over 600 fps and will disintegrate at over 700 fps. You would think that duct seal would change the game. But once you get the duct seal seasoned with pellets, an incoming pellet is as likely to hit an embedded pellet as duct seal and disintegrate.

    I’ve sort of discussed this away in my mind by supposing that pellet dust is mostly contained between the paper targets and the duct seal, vacuuming up stray pellets and debris from inside the trap that falls out, wearing an S95 surgical mask when I handle the trap, washing hands thoroughly when I’m done, and opening the windows and running a fan when I’m not shooting. Still, the lead is a cause for concern.

    Regarding the airplane problem, I finally realized I could cut the wire with the offending bead and remove it that way instead of destroying the bead. So here is further proof if any were needed that using fire and sword is probably not the best way to solve a mechanical problem. However, I was thinking that isn’t there some sort of gunsmithing tool that can cut new notches in screws that have had the original ones warped? Is it called a Dremel? That sort of focus and power might have been the very thing although I’ve discovered a better solution.

    Matt61



  14. I just now got an infomercial email from Pyramydair about their new AirgunArena site. Now what am I going to do? I already spend an inordinate amount of time on this one, how am I supposed to partake in two? Hmmm…”Choices”! Who am I? Which one is the right one for me? And I thought getting an airgun would be simple.

    BTW, there’s a pic looks like Tom with one of his fancy PCP air pistols. Looks like a man to be feared. The site can’t be too bad with BB there. Will you still be known as BB there? How are you going to wean us off this site? :)

    Looks like they’re offering Postal matches on the site. Now, that piques my interest.

    -Chuck



  15. CCI – CB longs – the answer to the question nobody asked.

    Out of a 6 ½ inch revolver barrel the average of 6 shots is 540 fps with a 29 grain bullet. Energy wise that is 18.7 ft lbs.

    Certainly not a toy, but nothing compared to the 135 ft lbs of a high velocity .22 LR out of a long gun.

    BB – if you can make a 10/22 run on these, you the man.

    Volvo


  16. For pellet impact sound deadening, I use a half inch thick sheet of modelling clay in front of a stack of 2/3 magazines or thick cardboard stacked inside my pellet trap.

    This has several advantages:

    [1] The obvious – It deadens the sound.
    [2] The clay catches any lead debris.
    [3] The magazines take the impact and disintegrate, leaving the clay intact.
    [4] The pellet trap can be used with magnum air rifles as they hardly take any impact.

    I’m sure many of us have tried this.

    Mo.


  17. Cjr:

    In re to your question yesterday about duct seal. If you haven’t found it yet, when you go to Menards or Home Depot or where ever, you have to go to the electrical section where they have all the conduit otherwise nobody will know what you are looking for. Ask for “that putty stuff used to seal around junction boxes.” Home Depot is about $2 for a one pound brick. You can go here to get a better idea of what to look for.
    http://www.telephoneparts.com/index.cgi?pcode=CI-DUCT-1

    Rabbitt


  18. For BBs, hang 5-6 sheets of carpet spaced about 1.5″ inside the trap. They never ricochet or make any noise, except the bb fallin down and rolling on the trap.

    Mo.


  19. Rabbitt,
    Thanks for the duct seal info! Now, maybe I’ll have more success when I go asking. I did look it up on the internet but it looks like shipping costs will double the total.
    -Chuck


  20. I use aguila super colibre about 12 ftlbs rounds in my 10/22 original clip. I keep one empty casing on the bottom of the clip because the last round won’t feed. Cycle it manually is really easy. Just remember to check to make sure the barrel is clear before going back to higher velocity rounds.

    CCI cb longs are my favorite cb cap and will feed in larger clips like steel lipped clips (made by buttler I believe) but not ram-line. Bolt action is ok, but tube fed multi-fed rifles work the best. I think remington makes an auto fed rifle that will work with shorts, longs and LR. The cci cb longs claim to run about 710 fps at 34 ftlbs.

    Aguila makes a pretty flat shooting 30 grain 1750 fps 204 ftbs round and cci velociters have some good punch.

    I’ve got boxes of sub target ammo to go through and some 60 grain SSS aguila rounds left over.


  21. Chuck -

    Go to the electrical section of your local Home Depot. You’ll probably have to ask for it – it was buried in the area with the “pro” grade tools, but it was there.

    The electrical guy at my Home Depot knew just where to find it, though he did look at me a little strange when I bought an entire case (10 blocks). Works fine!

    Phil


  22. CJr. I am sure you will find it now.

    I’ve mentioned before that I use it in my Crosman 850 Pellet trap. I used about 5 1/2 of the one pound bricks. Works like a charm. I tend to clean the pellets out rather than leave them in there but to each his own.

    The guys at my Home Depot also gave me a strange look when I told them what I wanted it for.

    Rabbitt


  23. Quiet:use the eggshell crate style foam mattress pads from wally world etc.in the cardboard box,cheap and easy to cut to size.Next put a thin wafer or press board on bottom of box so you can mount it on an adjustable camera tri-pod for multiple target angles:)

    BB I just used a lighter recoil spring in a marlin mod.60 to cycle
    CCI CB Longs. works almost every time:)
    THIS IS NOT RECOMMENDED but I use Aguila Super Colibri in a Henry .22 LA,just have to remember to clean the chamber.Quieter than my 953 and works good on close range small pests.Be aware of surroundings cause those 20 gr.conicals like to bounce!

    JTinAL




  24. I was in Gary’s shop last week. The “ballistic Mailbox” is the pellet/slug trap. The “Muzzler” is the sound attenuation device that the gun’s muzzle is placed in. The “Muzzler” does not look like the box you have pictured nor does it rely on fiberglass insulation for quieting. In fact, the muzzler has no fiberglass in it at all.


  25. Gary’s shop,
    Get back there and get the specs. Inquiring minds want to know – about both traps.

    Rabbitt/Phil,
    I went to Menards and their duct seal is a spray can of insulation. I went to Lowes and theirs is a bucket of stuff that reminded me of pipejoint compound. I went to Home Depot and bingo there it is. The clerk and I had to look on the shelves twice because we were looking right at it but didn’t see it. They only had 4 left so I got ‘em all. I’ll go back next week and buy out their restock.
    -Chuck


  26. Do shorts still erode chambers? Time was, the priming compound in the rim had crushed glass in it, but I think that’s changed.


  27. Well I guess there have been some changes in Gary’s shop since I was last there! The term “Muzzler” was not in use then and the Ballistic Mailbox was named by Gary because it resembles a mailbox in a pole.

    The times they do change.

    B.B.


  28. I was always under the belief that the heat of the gas was the cause for erosion in front of the short case. Every rifle has an eroded leade after many shots for the same reason.

    B.B.


  29. Hi all,
    Interesting subject BB. How about making the enclosure surround your chrony, with a triangular holes a little smaller than the rods that support the difusers. Could use some steel in the lower front section, ie. no more "shot chronys". I think the 'egg-shell' foam mattress pads would work, or could get fancier with readi-made acoustic foam products.

    At work we have semi-anechoic rooms large enough for diesel engines or entire earthmoving machines. Walls & ceiling were foam pyramids. Wrapped engines with lead-lined foam. It is a strange sensation to go inside and stand next to a 500hp engine that was quiet as a sewing machine.

    Here is a link to see something similar. You can enlarge the pics to see the foam pyramids closer. http://en.wikipedia.org/wiki/Anechoic_chamber

    Here are a couple links to foam materials.
    http://www.zzounds.com/item–AUR2WD01CG
    http://www.thermalfx.com/merchant2/merchant.mvc?Screen=PROD&Product_Code=SAAF&Category_Code=CASACC&Store_Code=T

    Cheers,
    OldOne


  30. B.B.,

    As I am shooting the P1 more and more using the air rifle scope and about 8″ of eye relief I am closing in on the 3/8″ groups, but in order to get there I think it would really help if that trigger could be brought down to under 12 ounces.

    In reading so much of what you have written about this P1 and about repairmen and tuners, I think that you said John Groenwald was The Man for tuning the P1, but I can’t remember and I thought rather than reading about 1/2 hour of stuff all over, I would just ask you.

    I remember that when you put his phone # out you gave the wrong # and some lady got rather upset about all the phone calls that she started receiving once the phone # started going around the internet.

    So make sure this time, if he is still The Man, to please give the correct #.

    Thanksalot.

    - Dr. G.


  31. RE: Lead Dust

    Matt,

    I wouldn’t be too worried about the lead dust. It is of some concern, but lead is really common. Anything that contains calcium will also contain lead. So if you drink a glass of milk before shooting you will get more lead from the milk than you will from shooting.

    An antacid with calcium carbonate would be “loaded” with lead.

    After shooting, or handling the pellet trap, washing your hands is an absolutely prudent and practical precaution before eating or food preparation. Same thing if you pump gasoline, have been painting, or scooping the cat’s litter box.

    From what I’ve seen in my pellet trap with duct seal, the pellets tend to melt on impact with each other not fragment into a powder. Higher velocity pellets into a solid steel deflection plate might be more problematic in creating lead dust.

    My impression is that it is good to have the trap inside a box. Bits of duct seal and paper get splattered around. The box contains the mess.

    Overall I’d hope that you don’t smoke and that you wear a seat belt when in a vehicle. Two practical considerations that would be vastly more probable to cause problems. The trick is not to get to paranoid about a particular risk, but evaluate your overall risks. Also don’t focus on risks that you can control and ignore those you can’t. We’re all at a substantial risk from drunk drivers for example. Hopefully the treat of a drunk driver won’t cause you to stop driving.

    Herb


  32. Herb,

    Thanks for the reassurance. I suppose that impact surface is as important to pellet disintegration as velocity and it make sense that lead would not cause as much disintegration as steel.

    Matt61


  33. With the Benjamin tank, is it possible to fill the disco to less than the regulated 2000psi? I heard that the sweet spot was around 1800, plus it would probably allownl for more fills.



  34. Jersey John,

    To do what you ask requires a gauge on the fill device. The device Crosman offers for their Benjamin tank doesn’t appear to have one, so that won’t work.

    You need to fill using a gauge, so I guess a scuba tank or a hand pump is the solution. That was how we designed the rifle. The Benjamin tank was an add-on and Crosman thought they would make it failsafe by putting in a reg without a gauge.

    However, don’t ASSUME anything! These small gauges are woefully inaccurate, so you can’t really tell where they are actually reading. A gauge is only useful when used in conjunction with a chronograph on a particular rifle.

    B.B.



  35. This is me Anatoliy!
    Thank you Tom for your greate advice. I surely will try to make that box.
    I actually thought you forgot about my question but I was pretty amaized when I saw your article this morning.
    I have found used car tires and stacked the up together and tried to shoot through those. It did helped a little and it made funny chambering sound.
    I will try the isulated box idea.
    thank you once again


  36. Anatoliy,

    Filling the tires with insulation would probably eat up most of the sound from the muzzle, and would be an exceptional piece of red-neck engineering.

    I had to post something here because the word verification was “burpo”.


  37. Anatoliy,

    I didn’t forget about you, but I was concerned that this box MIGHT be viewed as a silencer. After some careful research, I’m pretty sure it is not, but I didn’t want to do the wrong thing by writing about it, if it turned out to be illegal.

    I’m glad you finally got to read it. I promised to you the next Monday when I wrote it about six months ago.

    B.B.


  38. I just made one of these boxes out of an air conditioner duct that is about 13″ x 17″ and I cutted it to 22″ long. I covered both ends with the same material of fiber glass. It works great. I could not use my Daisy 008 pistol indoors because of the noise but I just emptied three CO2 cartridges and the noise was greatly reduced. Thanks for this great idea BB Pelletier!!!


  39. The silent pellet trap is easy – Home Depot electrical duct seal putty – 10# in a wooden box. The target sticks onto the putty. Cost me $25 plus some scrap wood.

    As I’m shooting an IZH46M pistol, I don’t have the noise problem.

    Our local Gander Mountain has a Gamo Whisper that may be handled, on a security cable. It shouldn’t be too hard to look at one and make a slip-on quieter that would never leave the privacy of the basement shooting range.


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