Discreet Ballistics Sets Out To Eliminate First Round Pop

If you are a silencer aficionado, at some point you have been effected by the dreaded silent killer known as ‘First Round Pop’. (Get it, “silent killer”). Present primarily within rimfire and pistol caliber suppressors while shooting subsonic ammunition, FRP is the result of oxygen trapped inside the baffles creating a mini explosion when unburnt powder is introduced during shooting. The phenomenon only occurs upon firing the first round because the oxygen is evacuated and not present for subsequent follow-up shots unless enough time has passed for oxygen to make its way back into the silencer.

The advanced ammunition manufacturer and quiet shooting lovers at Discreet Ballistics were sitting around on a classic New England Christmas Day, talking about silencers – my kind of people – when the topic of FRP came up. After a few hours of brainstorming and sketching, a now patent pending FRP eliminating system was born: the PopStop™.

Using an industrial-grade shrader valve device that mounts between the silencer and the barrel, the shooter uses a CO2 cartridge typically reserved for bike flat tire kits. With one short burst, the oxygen between the baffles is replaced with carbon dioxide, eliminating one of the fuel mixtures as well as any noticeable first round pop. The effect will last about five five minutes.

Discreet Ballistics – First Round Pop 

Now, I know what you are thinking. First off you are worried about a large, complicated system that will get in the way of your svelte host/silencer setup. Relax, this is a prototype – commercial versions will be smaller, lighter and lower profile. Second, you don’t care about FRP. Sure, the Discreet Ballistics device won’t be for everyone, but there are enough subsonic nerds in the U.S. who chase ultimate suppression to make it a viable idea. Lastly, yes you could use a liquid ablative, but that technique can get messy in a hurry.

Plans are in the works to produce both stainless and titanium versions in both 1/2 x 28 and 5/8 x 24 thread pitches. Official pricing won’t be finalized until the first units are available for sale, however the hope is to keep the stainless steel model around the $100 mark.


The Sionics M14SS was some of the inspiration behind the design of the Discreet Ballistics PopStop.

As I have stated many times in the past, I love simple, unique designs like this that solve real-world issues. I’ll be sure to keep you all posted on Discreet Ballistics progress but don’t forget to check out their lines of precision subsonic ammunition.

For more information on the PopStop, click here.

First Round Pop


LE – Science – OSINT.
On a mission to make all of my guns as quiet as possible.
Twitter: @gunboxready
Instagram: @tfb_pete


  • Dan

    Well I patented my own: Just pour a little Perrier or Diet Coke (as you would water or wire-pulling gel) in there before you take the first shot. A few shards of dry ice work REALLY well. All the solutions introduce enough CO2 into the silencer to work. Real Coke puts sugar in there, so don’t do that.

    • Canman

      Buy a quality silencer like a AAC or Dead Air and you don’t need this gadget. Great invention for the Silencer Co Sparrow that has huge FRP I guess.

  • jonjon7465

    A must have for assassins. I never cared enough about it.

  • Lew Siffer

    AAC got rid of FRP a few years ago with their Element 2. No goofy gimmicks and no pouring water or squirting gel. I have no idea how they engineered it but their baffles alone make the first shot as quiet as the rest.

  • Anonymoose

    Just in time for the next James Bond movie!

  • PK

    Good luck on the patent, guys. This was openly discussed on forums as far back as 2006, if I recall the date correctly. It’s kind of difficult to patent something which has been in the public sphere for over a decade.

    • BeGe1

      Actually, if I recall correctly, under the Obama administration the patent system was changed from a “he who invents it first” to a “he that files for patent first” system.

      I could be wrong on that…but I think I remember reading an article on the topic and being quite disgusted, because the main reason for such a change would be to favor big businesses over little inventors.

      • PK

        If something is in the public sphere, it’s really difficult to successfully defend if you attempt to enforce the patent in court. They’re welcome to attempt it, of course, and I wish them luck.

      • Nope. Most nations are first to file, but we are stuck with first to “reduce to art” due to the language of the constitution.

  • Jimijam04

    What a gimmick. No wonder they put it on the Q El Camino – It has almost the worst FRP in history.

    • DiscreetBallistics

      The Q El Camino is an awesome can. The FRP is minimal with it. It just happens to be coupled with it in this picture

  • Kimberwarrior45

    I am confused. Gunpowder does not need outside oxygen to burn (the oxygen in chemically attached to the ‘powder’ and released when energy is applied thereby allowing it to burn). If there is unburnt powder in the suppressor it should not require oxygen for combustion

    • Dan

      I think it’s compressing the oxygen already present in the air and igniting that. Doesn’t seem right though so maybe i misunderstood what’s going on.

    • gunsandrockets

      Excellent observation.

      Perhaps FRP is not from burning gunpowder. Perhaps accumulated gunshot residue in the suppressor burns in the presence of oxygen. That residue might be from many sources: gunpowder combustion products, bullet dust, maybe even dust from the suppressor itself?

    • Could be BURNT powder residue (carbon), which DOES need an external oxidizer, that’s providing the fuel for FRP…

    • Blackhawk

      Gunpowder has an oxidizer in it, but it isn’t always an exactly balanced amount of oxidizer and fuel. It’s possible there’s an oxygen deficiency in the powder (which would make sense with all the residue in dirty guns), and the oxygen allows that to burn. It’s the same idea as muzzle flash, except with the bare muzzle we can’t hear the flash over the sound of the gunshot. That’s just my theory based on the chemistry.

  • Brett baker

    Other than spec ops, who really gets freaked about frp?

    • pun&gun

      Probably people who like to shoot without plugs or muffs and worry about the pop going above the hearing-safe threshold.

    • ActionPhysicalMan

      Not wanting it and getting freaked out about it are two different things.

  • Jtx

    Just stick your lips to the can and blow down your barrel, in reality the silencer nerd won’t be happy til they are shooting in space where nothing makes a sound

    • Sledgecrowbar

      Please don’t apply the muzzle of a firearm to your mouth.

      • Old Tofu

        blow in silencer , then apply silencer to handgun

    • Nashvone

      Too many people are already enjoying Kurt Cobain lollypops without this absurd suggestion.

    • DiscreetBallistics

      This is exactly why we doing this – to avoid dangerous/damaging methods of quieting one’s can.

    • DiscreetBallistics

      This is exactly why we’re doing this. We want to give folks the option of quieting their can without being dangerous (blowing the can) or distructive (adding liquids to the can). And yes, I’m a proud silencer nerd

  • Jeff Brown

    I’ve being using suppressors for 30 years and never experienced or heard of this. Not convinced.

    • DiscreetBallistics

      What would convince you that this device eliminates FRP?

      • Old Tofu

        he’s saying he doesn’t believe in FRP , hasn’t experienced it , solution looking for problem

        • Jeff Brown

          Correct. Hearing is believing.

  • Forest C. Adcock

    Wouldn’t it be MUCH cheaper to just get a plastic tube I could insert through the bore and fire off the co2 with?

    • Sledgecrowbar

      If you took a schraeder valve and attached a hose to it, you’d be there. Those flat kit inflators are awesome, they will hold pressure for ages in a little CO2 cartridge and they have a nice fire extinguisher-type trigger. Sticking things down a loaded barrel isn’t an ideal endeavor, though.

      • Michael Gallagher

        Then don’t stick it down the loaded end of the barrel. Go from the breech end before chambering a round. It’s not like the effective time from treat to fire is real short. You could also spray the non-flamable gas into the chamber, forcing the air out the open end at the muzzle, place a piece of electrical tape over the muzzle trapping the gas inside, load a round and probably have a set up that would last quite a while before oxygen seeped back in.

        This gimmicky tool and attachment is not the answer to this issue. Go a simpler route.

      • RShanger

        So wouldn’t it be easier and cheaper for them (or anybody for that matter) to use one of those instead of what is essentially an adapter? The thing I don’t like about this design is that it uses an adapter that might not be concentric.

        • Sledgecrowbar

          Manufacturing something with concentric threads isn’t difficult. I return to my previous statement that sticking your hand, or anything, in line of a loaded barrel is dumb. Sure, you could get a 90-degree tube to keep your fingers out of the way of the bore, but you’d still be obstructing it with the hose and an obstructed bore is a good way to ruin the hand you’re holding the gun with. There is no good way to do what you want to do. This might be 20 times as expensive, but it doesn’t disobey any core firearm rules.

          • RShanger

            I get what you are saying, but I think most real suppressor owners are aware of said fact and already know to stage a can before attaching it or with an unloaded and locked back action. I guess I should have alluded to that before hand. Regardless, the way I see one of those bike inflators being best used is like a typical aerosol based media.
            Spraying it through the can with a long nozzle through the barrel of said pistol/rimefire can.

          • DiscreetBallistics

            The problem with a locked back action is you don’t have a good seal from a chambered round. Much of the pressurized co2 if injected in the muzzle of the can will leak out of the action

          • RShanger

            Either way there will be pressurized Co2 leaking out unless you cap the end cap with a piece of tape or a wipe.

            I think I will just stick to my method of a touch of gel and a piece of tape on the endcap. Unless proven other wise or if I see it my self, I wouldn’t feel comfortable with an adapter on my suppressors that I waited months for just to chase a few meaningless dBs.

          • So long as you have a round chambered before you spray.

          • RShanger

            Why would I willingly chamber a round then stick my hand in front of the muzzle? That’s what I’d want to avoid doing.

          • Christian Hedegaard-Schou

            Uh, just run a short tube down the chamber with the slide locked back. Give it a 2-3 second spray, release the slide, shoot.

            You can do this right now with almost any emergency tire inflator available on Amazon, and never violate any rules of firearm safety.

      • DiscreetBallistics

        We though of that and at this point we just wanted to make the device as simple as possible. If the market demands it we’ll do a more integrated design

  • FLdeepdiver

    So a common can of compressed air from an office supply store would do the same? -Asking for a friend

    • Mark-in-Indy

      Yes. Yes it will.

      • Phillip Cooper

        Not necessarily. Some of them are flammable.

        • Sledgecrowbar

          All of them are flammable, so this would have the opposite effect and make a louder first round pop. Also sticking something down the bore of a loaded gun violates a core safety rule, putting one or both of your hands at risk.

          • DiscreetBallistics

            Squirting, pouring, or squeezing any substance down the muzzle of the suppressor, especially with a chambered round is not a great idea

          • Phillip Cooper

            Well, some of them require it, apparently- wet wipes and all that sort…

          • AlDeLarge

            It’s a gas, not a liquid or grease as used in wet suppressors, not a foam like Inland Manufacturing dB Foam For Silencers. You could always spray it in from the chamber side before chambering a round, if you’re concerned about putting your hand near the muzzle.

          • Phillip Cooper

            You kow flexible straws are a thing, right? You wouldn’t have to put your hand in front of it, and you could just as easily juice it before loading the weapon.

            You’re telling me you NEVER point the barrel at your hand while you’re cleaning the weapon, either? Doubt it.

          • FLdeepdiver

            Not all. Just search “office duster non flammable” in google. You will see it available at Walmart for $5.

    • Badwolf

      No no no. Compressed air dusters contain difluoroethane which is flammable. But even if it’s just compressed regular air then it still has oxygen.

      • BKS

        Difluoroethane, flamable or not, will displace oxygen. If oxygen is the cause of FRP, problem solved. Besides, any compressed or liquified gas as it expands, it refrigerates.

        • Until more air runs in because you set the gun down for a second, or popped the breech open to handle a misfire, and reintroduced air into the system.

          At which point you have a volatile flammable, air, and an ignition source. Blowing your can up like an M-80 in a mailbox is likely to be exciting, hazardous, and expensive…

          • Rick

            The first shot will remove the canned air too. It works for me. Use at your own risk if your scared.

        • Badwolf

          You’re absolutely right. Oxygen causes FRP. DFE will displace oxygen, and probably cause first round kaboom. Problem solved, at least it’s not a pop.

    • BeGe1

      Well if it’s actually compressed “air” then what have you changed? You replaced the air from the atmosphere with the air from the can. Both have oxygen.

      This is specifically compressed CO2, which is 1) not air, in that it doesn’t have oxygen in it, 2) not some flammable gas like many other compressed gasses may be

      • noob

        could it be the cooling effect of expanding gas chilling the silencer? sometimes “running wet” causes a db reduction because the hot gasses are rapidly cooled on entering the silencer and lose energy heating up the silencer.

        What happens if you hold the CO2 can upside down so liquid CO2 and dry ice enters the silencer? an even quieter first round shot or a kaboom?

    • Rick

      I have been using a common air can from the store for some time. Its worked for me. But i am sure these co2 cartridges are even better.

  • iksnilol

    Or just use some water ?

    Just use a spray bottle or something.

    • DiscreetBallistics

      Water is messy and can be corrosive depending on the material used

  • Kelly Jackson

    I guess I don’t get the point.

    I mean it’s a neat concept, but it’s also vastly complicated for something that’s really a non-issue.

    What are you doing with this gun that the first shot needs to be as quiet as the rest? Because for the majority of us we’re just dicking around at the range

    • koolhed

      Neighbor’s cat. Don’t want to wake ’em.

    • DiscreetBallistics

      We want to make silencers as quiet as possible. FRP can put certain silencers into the 140dB+ zone which can result in permanent hearing damage

    • BeGe1

      Some people’s lives depend on their firearms.

      Cool that yours doesn’t…but it doesn’t have to apply to you for you to get the point of it.

      I know for a fact that at at least one point in modern history SEALS were using suppressed rimfire pistols for sentry elimination. Being able to reliably count on not getting FRP could literally save their lives. Seems like that might be worth it to them.

  • DanGoodShot

    I’m sure you could extend that five minutes of the effect by simply placing a cap over the end of your suppressor. Just be sure and remember to remove the cap before going ‘bang’.

    • DiscreetBallistics

      Our tests have shown this to be correct. You just need to have a chambered round (seal)

    • Christian Hedegaard-Schou

      Or use a sacrificial “cap” that you can safely shoot through. Like a piece of masking tape.

  • Matt O

    Frp seems to be fixed by using a smaller blast chamber, but this causes extra wear/stress on the first baffle. Balancing blast baffle toughness with a small chamber seems to be what the people who make great cans are doing

  • Raoul O’Shaughnessy

    “at some point you have been effected”
    Or ‘affected’, even. “Affect” vs. “Effect” is right up there with “Flaunt” vs. “Flout” in terms of Journalism 101 basics. A used AP Stylebook can be had on eBay fpr ten bucks.

  • Deadlyplatypus

    Why not just design it to allow the user to insert replaceable diaphragms at the thread end and muzzle and then pull a vacuum on the can? You wouldn’t need to do it immediately before firing and it would likely make it even quieter since combustion gasses could actually expand even more inside the suppressor. Just a thought…

    • The diaphragms would be “silencer parts”, so you wouldn’t be allowed to keep spares.

  • rugerno1fan

    To quote Bob Bulldog Briscoe, “Well that’s up there on the dork meter.” Like PK I wish them well on this wild journey they’re on!

  • Martin T

    Dear god I can’t wait to start operating!

  • FLdeepdiver

    made my day. Also, how did you get links to work?

    • Sausage

      Cut and paste…….I have 6 cans of the stuff and use it on my 17 HMR and 22 lr. Not only does it get rid of FRP, it stops the first shot flier too,

    • AlDeLarge

      Copy/paste and hope the moderator eventually gets around to approving it some day.

  • Christian Hedegaard-Schou

    Why does this require an adapter between the muzzle and can?

    Why can’t you just take a regular CO2 tire inflator with a small hose attached and with the slide locked back, do a 2-3 second burst of CO2 down the bore via the chamber?

    Release slide, chambering round, fire. No FRP.

  • Bruce

    I can accomplish the same thing by locking back the slide and purging the entire barrel/suppressor area with CO2 without adding another part to my suppressor that I’m not allowed to buy parts for.

  • MarcoPolo

    I’ve got two different suppressors, never noticed a first round “pop” with either. Perhaps I’m doing it wrong.

    • Federalist

      Yeah, I can’t hear it either. I recently did some testing with a Larson Davis LxT1 sound level meter and I could see in the data that the first round through a cold, dry suppressor does in fact peak 3-4dB louder than subsequent shots, but for impulses like subsonic shots I don’t believe that’s within the capability of the human ear to distinguish.