The Rimfire OUNCE Pistol by Third Bay LLC

    The Rimfire OUNCE Pistol by Third Bay LLC (4)

    Ounce pistol in folded (left) and ready to fire states.

    Third Bay LLC‘s Ounce pistol was the most unusual non-prototype firearm this author saw at the SHOT Show 2022. Everything in this pistol is unusual for a semi-auto rimfire handgun – from the action type to the feeding mechanism and its folding design. We briefly talked about this handgun in our Rimfire Report article dedicated to the best rimfire guns from SHOT Show. In this article, we’ll take a more in-depth look at this obscure semi-auto rimfire pistol.

    Rimfire Handguns @ TFB:

    The Ounce pistol is a hammer-fired locked-breech semi-auto handgun chambered in .22LR. The integral magazine is located above the action and it holds 10 rounds of .22LR ammunition. The magazine has no spring and feeds the cartridges into the action via a transporter powered by the cycling action itself. The spent cases are ejected downward through the hollow polymer grip. To load the magazine, one must open the side gate and place the cartridges as shown in the picture below.  A more detailed description of the loading and disassembly processes can be found on the company’s website.

    The Rimfire OUNCE Pistol by Third Bay LLC (3)

    The action is rather unusual for a rimfire gun – it is a long barrel recoil action (like the Browning Auto-5 shotgun or Chauchat machine gun). In this type of action, the barrel and bolt recoil locked together to the rearmost position where the action gets unlocked allowing the barrel to move forward while the bolt is held back. On its way forward, the barrel strips itself from the fired cartridge case which is held on the bolt face and gets ejected as soon as the barrel clears it. Upon reaching its foremost position, the barrel trips the bolt which starts moving forward feeding a new cartridge into the chamber and closing the action. What’s the point of having a long barrel recoil action in a .22LR gun? There are several advantages. The long recoil action is cleaner because fewer residual gasses are blown back into the action due to the longer time from firing the cartridge to opening the action. Another advantage is that the felt recoil is minimal. Not that .22LR has any significant recoil but this pistol was designed to make it easy to shoot for literally anyone including people with very weak grip strength. Last but not least, this action type allows making the gun as lightweight as a semi-auto .22LR pistol can possibly be because unlike blowback guns (the most common action type of semi-auto .22LR firearms), the long barrel recoil action does not rely on the bolt weight to cycle. The bolt of the Ounce pistol is a blade-shaped part resting alongside the barrel and it weighs next to nothing.

    The Rimfire OUNCE Pistol by Third Bay LLC (2)

    Ounce pistol with side plate removed and magazine gate opened showing the layout of internal parts.

    Talking about the weight, the pistol is named Ounce not because it weighs an ounce but inspired by the following Benjamin Franklin quote: “An ounce of prevention is worth a pound of cure”. The overall weight of the Ounce pistol is 7 1/3 oz unloaded and 8 1/2 oz fully loaded. The Ounce pistol is also very compact. In the open/deployed state, the overall length of the gun is 5 3/4″. When folded, the barrel/breech assembly retracts into the frame shortening the length of the folded gun by an inch (4 3/4″) which is only an inch longer than the barrel length (3 3/4″).

    The Rimfire OUNCE Pistol by Third Bay LLC (1)

    Barrel/bolt assembly removed from the frame.

    The Ounce pistol has no manual safety but there are a number of safety features incorporated into the design of this handgun. When the gun is folded, it is virtually impossible to fire it even if there is a round in the chamber because not only the trigger is disabled in the folded state, but the firing pin is not aligned with the cartridge rim so even if the firing pin is hit, it won’t ignite the primer of the chambered round. The pistol also has a loaded chamber indicator.

    The Rimfire OUNCE Pistol by Third Bay LLC (5)

    Ounce pistol’s ejection port – the spent cases are ejected downward through the grip.

    The Ounce pistol is designed to be easy to manipulate and fire. Due to the lack of a magazine spring, it is very easy to load the integral magazine. Despite the compact size, when it’s deployed, the pistol provides a full grip making it easy to control. Additionally, the low barrel axis along with the recoiling action contribute to its controllability. The lack of manual safety makes it faster and easier to make it ready to fire in a high-stress situation. Charging the gun is done by folding it using the handle as a lever to compress the springs. The gun is also extremely easy to deploy from the folded state as it springs open in a matter of pressing a button. The action of the Ounce pistol cycles within the frame with no parts extending behind the frame which means the cycling action won’t interfere with the shooter’s hand causing an injury or malfunction.

    The Ounce pistol is listed on the Third Bay LLC’s website at an MSRP of $899. The estimated start of shipping is late spring 2022.

    I think this is a pretty interesting concealed carry concept if it operates reliably. It’s extremely easy to use, conceal and packs quite a firepower for a handgun of this size. I am sure many of you are skeptical about the reliability because the internals look like a clock mechanism, but maybe it also runs like clockwork!? What would possibly make this an even better close quarter defensive tool is some sort of barrel shroud that retracts into the frame when the pistol is folded but locks on the frame when the gun is unfolded working as a standoff device.

    I hope you guys enjoyed reading about this little engineering wonder. To learn more about the Ounce pistol, you can read the patents protecting the design of this handgun: US9945629B2; US10422600B2; USD756478S1; CA2970349C.

    Many thanks to Bill Osborne, the inventor of this pistol for explaining the features of this handgun to the author at SHOT Show 2022.

    Hrachya H

    Managing Editor

    Being a lifelong firearms enthusiast, Hrachya always enjoys studying the history and design of guns and ammunition. He also writes for and
    Should you need to contact him, feel free to shoot him a message at [email protected]