Winchester Introduces 3,000 fps Rimfire Cartridge

Winchester officially announced the .17 Winchester Super Magnum cartridge today, and it does appear to be the fastest and most powerful rimfire cartridge ever. Two flavors have been announced so far; a 20-grain bullet reaching 3,000 feet per second, and a 25-grain bullet traveling at 2,600 feet per second. Muzzle energy on the 20-grain loading is rated at 400 foot pounds, with the slower 25-grain loading measuring 375 foot pounds. By comparison a standard 115 grain 9mm Luger round generates around 330 foot pounds of muzzle energy, so this sort of performance from a rimfire is a true breakthrough. Case capacity exceeds any previous rimfire caliber, and the latest generation ballistic tipped bullets will be utilized immediately in factory loadings. Suddenly, it is realistic to score a humane kill on a coyote sized game animal with a rimfire rifle, every time. Accuracy is said to be very good, but the cartridge’s true claim to fame will be its ability to resist wind drift significantly better than .17 HMR or .22 Magnum. Effective range is well beyond 200 yards.

17 Winchester Super Mag

The most interesting thing about the .17WSM may be the casing it uses, which doesn’t come from a firearm at all. Winchester manufactures .27 caliber rimfire casings already for use in powered fasteners (what we rednecks call “nail guns”). What effect this will have on the cost of the new cartridge is unknown, but the pundits are agreed that any new rimfire caliber needs to be affordable or its chances of success are slim.

With these numbers and Winchester’s name on the cartridge, expect multiple manufacturers to offer rifles chambered in .17 Winchester Super Magnum before the end of the year. Will the .17WSM be suitable for semi-automatics? With the chamber pressures involved in firing a 20 grain bullet at 3,000 fps, I would guess that a simple straight blowback design would not suffice. A rifle with a gas operated locking system would be needed. An AR-15 style varmint rifle chambered in this caliber would be a terror to groundhogs.


  • Brice

    Well, I wouldn’t want to fire .308 rounds from a straight blowback, but a delayed blowback ala H&K, already been done. Heck, if you’re brave, you can get a Hi-Point in .40 S&W, that’s straight blowback.

    • GreenPlease

      The problem with roller-delayed blowback is cost (way more expensive than simple blowback and more expensive than DI gas or gas piston) and reliability. IMO, both gas piston and DI designs are more reliable than RDBB, ceteris paribus.

      • Esh325

        You think that they could make a 7.62×39 or 7.92×33 simple blowback today that wouldn’t need any special accomdations like flutes in the chamber,etc? I’m saying this because I’ve seen them make simple blowback 5.7×28’s which have higher chamber pressures than a 7.92×33 or 7.62×39. You could make a very reliable and inexpensive rifle that way.

      • noob


        I’d worry about the bolt thrust more than directly comparing chamber pressure. You can have a high chamber pressure but the case geometry and materials can result in a surprisingly low bolt thrust which then means a less “strong” operating system (like direct blowback) can be used.

        for instance, all other things being equal, a straight walled case will generate less bolt thrust than a tapered case because the tapered case will separate from the chamber wall earlier.

      • Mu

        That must be why the MG42 was known throughout WWII for its low performance while everyone just loved the M16 in Vietnam for its superior reliability.

      • Esh325

        It’s not really fair to compare a heavy beltfed light machine gun in 8mm Mauser, to a magazine fed light weight Assault rifle in 5.56×45. The MG-42 is not even a roller delayed blowback, it’s roller locked recoil operation. Apples and oranges. A more fair comparsion would be a HK33 and G41 vs a M4 and M16A2 or an AR-10 vs a G3 rifle. As far as which would be more reliable, I couldn’t really tell you.

    • GreenPlease

      This would be quite remarkable if ammo was only, say, 25% more expensive than .22lr. I’m pulling for them.

    • El Duderino

      The bolt on a .308 pure blowback would weigh 20+ pounds and have a recoil spring you could use on a Jeep Wrangler’s coil suspension. Not really practical.

  • fred johnson

    A rimfire version of the .17 Hornet?

    I do have a real question for the varmint shooting crowd. What is the advantage of a 20 grain bullet like this new Winchester round over just getting a varmint gun that shoots .223 Remington? Lower recoil?

    • Marc

      Lower costs.

  • Tom – UK

    Does anyone else think that there are too many calibers on the market at the moment?

    It seems like every manufacturer is coming out with some new fangled caliber at least once a year. Now don’t get me wrong I love that market forces push for useful things to be made but a large number of these calibers don’t really seem to do anything particular in my humble opinion.

    Take for example 6.5×55, 7.5×55, .270, .280, 6.8 sps, and 6.5 grendel between them there are differences between weight and speed in all of the calibres which shoot between 90 and 180grain bullets but really is there so huge a difference? could 2 of those calibers not do the same work as the rest of them put together?

    It just seems silly to pay the cost to have 6 production lines with all the machines, workers, packaging making 6 different types of rifles and ammo when there just doesnt seem to be a need for this great a level of diversity.

    I am ready to be corrected/educated though 🙂

    • Marc

      We could standardize on 4 center fire rifle cartridges covering everything from squirrels and plinking to big game and extended range target shooting. Also 1 rimfire and 1 handgun cartridge. I get to pick and you throw away most or all your old guns because ammo won’t be available, sound good?

      • Tom – UK

        I think your example is a tad drastic, however yes its nice to be able to feed all of our old calibers (I for one would know with my .303 British rifles) however the calibers I have listed above are being made in new rifles as well as existing ones, that is not simply feeding old guns it is continuing the issue.

        I think Simon has an interesting point but really who is going to use a 20grain bullet out beyond 200meters, is there much point paying for this whole new caliber (which is rimmed so not great for semi autos) if shooting at beyond 200m? Is there really a need to buy a whole new rifle and the ammo for it when an existing bolt action .223 would do?

    • Simon

      This new caliber would be useful in countries where centerfire rifles semi-autos have limited magazines and rimfire doesn’t. In Canada, for example, this caliber would be very interesting in a semi auto rifle with a 20-30 round clip since no centerfire semi autos can have magazines with more than 5 bullets in it.

      • Jerm


      • David/Sharpie

        I agree Simon, this would take advantage of the loophole regarding magazine capacity.

        I’d buy it depending on cost or gun, mags and ammo.

    • Pancho

      Rifle manufactures and ammo manufactures don’t have 6 different lines making these products. They have one line and the swap out the tooling. It’s 6.5 Grendel on Monday, .270 on Tuesday and Wednesday and so on and so forth.

      I will assume you are in the UK, just an observation. How many rifles do you own? I myself have lost count of the rifles I own. I could make due with only one or two but the great thing is I don’t have to. I can buy as many as I want. I even make my own sometimes.

      You may want to seek out education in economics and capitalism. What you are looking for is “utility” and “demand”. Socialist and Communist would advocate I one cartridge totalitarian system where the supply side or “command” side makes the economic decisions. Just saying.

      • Tom – UK

        Hi Pancho, I’m afraid my knowledge the manufacture of ammunition isn’t much worth talking about, the closest I can relate to is my large amount of reloading. I presumed that the level of demand for ammunition in the USA would require constant manufacture hence my belief in the several lines of production being needed.

        I own 5 rifles and 2 shotguns at the moment, have 2 years armed forces experience and have had the pleasure of using many club/friends rifles. Suffice to say im not clueless ;-), you can see me shoot on the youtube channel jubbles2343.

        Strangely I have managed to learn about economics and capitalism throughout life, I’ve even managed to make rather a lot of cash. socialism and communism have nothing to do with this, this is about we as consumers being told each caliber is “new/better etc etc” when it isnt, we can’t afford to buy several guns for several calibers and find that out and often the sources of information we have on guns n ammo such as magazines/forums/others experiences are not reliable as magazines are funded by advertising/sponsorship, forums are full of s**t/we don’t always trust what we read and when speaking to others we have their and our biases.

        This misinformation/lack of ability to determine the truth means that people do buy “the newest and best” or stick with older models too, its innefficient and results in higher prices. I just wish manufacturers would aim to provide a better service by perhaps feeding the guns out their already but choosing to stp producing pointless new calibers and guns in 5 different calibers that do the same thing.

      • Pancho

        Tom. Your complaining about a system of firearms design we have had for more than 200 years. Designers and engineers work to come up with something new. They don’t get paid for old stuff someone else invented. We as consumers only buy what is new and as much as 80% of some firearms companies sales comes from new products.

        Sometimes we get a keeper. Perfect example is the 375H&H it was designed to fit a niche for a hunter who wanted to have ammunition that fit both his bolt action and break action rifle. 22LR, 308Win 300Win Mag, were all marginal improvements over the products they replaced. (22Auto,300Sav an 300H&H)

        Winchester and Remington have been arch rivals for more than 100 years of course you are going to have this. The great part is we get to pick the winners but their are no losers.

        6mm Rem vs 243Win
        264win mag vs 7mm rem mag
        270Win vs 280Rem
        300 SAUM vs 300WSM
        220Swift vs 22-250Rem
        225Win vs 223Rem
        30Rem vs 30/30 Win
        351Win vs 35Rem

        Seems to me like you are more afraid of picking something that people on the internet don’t agree with.

        How does this result in inefficiencies? Again you should have paid attention in economics classes. The competition of these parties keeps the price down, plus you can get a really good deal on them if no one else likes them a few month down the road. I bought 400 rounds of 7mm WSM ammo with Fail-Safe bullet and nickel brass for $9 a box. I like 7WSM and I don’t care what the internet says.

        The socialism is oozing from your comments socialist use words like “inefficiencies”, they believe in mistrust of businesses, that corporations are telling you what to buy. I would hope that you are intelligent enough to see through the hyperbole of advertising.

        If you can’t afford a new 17WSM don’t buy one and you lose nothing or buy one shoot it and you still lose nothing. You got to shoot. And unless you don’t enjoy shooting, you are never wasting money.

        I completely disagree with you their is a huge difference between a 6.5×55 and a 6.5 Grendel. 6.5×55 doesn’t fit in an AR15. But people in socialist countries wouldn’t understand that so I don’t blame you.

      • Esh325

        Keep it easy on the chap, he just has a different opinion. Socialism? lol.

    • atm

      Those calibers you mentioned are the only ones still sitting on the shelf at the local Dunham’s.

      It would appear that a company could have one production line that rotates thru the low volume calibers, with dedicated lines for .223, .308, 9mm, 45, etc.

    • ThomasD

      Your utilitarian argument could be extended to just about anything – automobiles, homes, even restaurant menus.

      Many of us would still be just as happy, but someone somewhere would miss their tandoori flavored rutabaga crisps.

    • JMD

      It’s called capitalism. The market will decide what floats and sinks. Get over it.

    • Legman688

      New production rifles are being made in 7.5×55? Do please link to one, I’m fascinated.

      Also, the “problem,” if it is a problem, is in fact much ‘worse’ than your short list of, strangely mostly very old military cartridges, indicates. The group of sub-.30 calibers also includes now .260 Remington, 6.5 Creedmoor, .270 WSM, .25 WSSM, .25-06, 7mm-08, .257 Roberts and many, many more. I think the reason the .257 to 7mm/.284 caliber range sees so much proliferation is because cartridges in that range offer a great deal of versatility with flat trajectories and comparatively low recoil.

      Having said all that, I actually agree with your basic point. Cartridge proliferation has largely gotten out of hand. This is for one very simple reason: gunmakers, as of yet, cannot do planned obsolescence (unfortunately, they’re starting to get there). Thus in order to sell more guns they need to be able to claim that the new gun/chambering combo offers a significant benefit over existing cartridges. Hence, the new caliber every year.

      As for this new rimfire magnum, nothing about it sounds like a good idea. The structural properties of brass have not changed significantly in the past 100 years, nor has the need of rimfire rounds to have thin, soft rims. I forsee nothing but trouble. And frankly, I’d still rather have a centerfire, reloadable .17 if I wanted a sub-caliber varmint gun.

  • 7.62x25FTW

    “An AR-15 style varmint rifle chambered in this caliber would be a terror to groundhogs.”

    Isn’t a AR-15 style varmint rifle in .223 already a terror to ground hogs?
    What exactly ARE they trying to do here?

  • dustyvarmint

    I was just up at Cabelas selling my .204 Ruger in favor of a .223 due to the .204’s lighter weight bullets and wind drift. And the higher cost associated with everything .204. Just in time for the .223 rush.

    Anyway, the Gun Library guy said they get a lot of .204s and .17 HMRs in as they just didn’t catch on. I thought that was weird on the .17 HMR. I love my cheap-arse Savage 93R17. My buddy and I thought he may have meant .17 Remington?

    Happy shooting, dv

    • Pancho

      I worked in a gun store in the central valley of California. We sold hundreds of 17HMR’s when they came out. Biggest thing to come around in a long time.

      • Duray

        Those magic words: “when they came out.”

    • cdp

      My only question to this comment is what bullet were you shooting out of your 204? The 204 is SUPERIOR to the 223 in wind drift.

  • C3PO

    does anyone know how the bottlenecked rimfire cartridges headspace? Is it on the shoulder or the rim?

    • ThomasD

      I assume it is always going to be the rim – otherwise tolerances would need to be ridiculously tight.

  • Duray

    “Case capacity exceeds that of any previous rimfire caliber.” Pretty sure that’s flat incorrect. Open “Cartridges of the World” to the chapter on rimfires.

    • Pancho

      This is obviously a big concern that should be addressed with all of the .44 and .32 rimfire rifles and ammo on the market today.

    • John Doe

      I bet they meant rimfires that are currently mass produced, not rimfires made in some reloading wizard in his basement.

  • Bob H

    I wonder what the case head dimensions are? Wondering if all those .17M2 out there could be easily converted to .17WSM?

    • JMD

      .17 Mach2 is a .22lr necked down to .17. Not a chance those can be converted to this new cartridge.

      • Jake

        I take it that also means no .17 HMR > .17 WSM conversion either? It’s a shame. If anything was possible I’d ideally want a gun that could shoot both .17 HMR and .17 WSM, but of course now I’m just dreaming.

  • Pancho

    How is this not a viable option? It has the energy of a 22 Hornet and is within a few cents per round of the price to buy bullets, powder and primers for reloads.

    So if 1000 rounds of .17WSM ($16.25 as already advertised) is $325. Then take the 17 Hornet, so lets say you buy 200 rounds of new ammo so you have brass, then reload them 4 more times. $162.90 for new ammo it will take 1.1 pounds of powder, $22.58 for powder, $122.16 for 800 VMAX bullets, $20.55 for 800 primers if you buy all of this from Midsouth today. Throw in a set of RCBS dies and you are at $386.99 for the 17 Hornet after 1000 rounds. That is if you don’t count case lube, tumbler media and any other incidental additional supplies need to reload.

    This is centerfire performance that cost less than the cost to reload.

  • Bryan S.

    Lets see a PMR30 in this…

    • atm

      Take a gun that blows up and put a higher pressure cartridge in it? No thanks!!!

    • ThomasD

      I’d settle for seeing a PMR30 period.

      • El Duderino

        I have had one on order since the original design, it’s now on its 3rd revision I believe. Which really sucks since it will be a 10 shot gun in a couple months if our beloved leaders get their way.

  • seeker_two

    GreenPlease: IIRC, the reason CETME & HK developed the delayed roller-locking action was that it was simpler and cheaper to build than the gas-piston systems. In fact, the Nazis used that system on the MG34 & MG42 for that same reason. With CAD/CAM tech, it would be even more economical.

    • Lal

      If you use the term “in fact”, you should know what you are talking about.

    • Esh325

      That was true at first. It became more costly and less practical later on when it became more developed such as when they had to switch calibers to 7.62×51, the Spanish had to use higher grade steels which drove up cost.

    • Zapp Brannigan

      The MG34 and MG42 operate on short recoil, not delayed blowback which is how the G3 rifles work. The MG34 did not use rollers but a rotating bolt. The MG42 used roller locking which looks similar to the delayed roller bolt but functions differently.

    • El Duderino

      I think it’s all about weight actually. With the H&K delayed roller locking system you have to have a steel receiver and a heavy bolt + bolt carrier. I am not aware of a way to make the system lightweight. Look at a HK93 vs. an AR for instance.

      G3 pattern rifles are pretty inexpensive to make, anyone who has taken one apart can figure that out. All the parts are big and simple.

  • DW

    Imagine a 10/22 in this caliber…
    Poor man’s PDW?

    • Duray

      If they couldn’t get it to work in 22wmr, you can be sure this won’t either.

      • Komrad

        It worked, it was just too heavy and expensive to be very popular.
        I think Magnum Research makes .22 mag 10/22 clone.

  • chs

    As a neat FYI, an AR15 chambered in this would be 100% legal in California as rimfire rifles are not classified as assault weapons.

    Alexander Arms already has an AR15 chambered in .17hmr.

    • Brian in Seattle

      Do it! The sooner, the better!

  • Justin J

    While all you guys are arguing calibers and logistics, I’m here thinking, “Damn, that’s fast!”.

  • Most powerful rimfire ever? Please…

    Try that on for size.

    • It’s not even the fastest rimfire, ever, either. The 4.5x26R Interdynamic pushed a 1.58 g (24.4 gr) bullet at 1,000 m/s (3,280 ft/s) from the Interdynamic MKR’s 26″ barrel. What’s truly wild is that that cartridge, which was designed by none other than George Kelgren, produced a chamber pressure of over 70,000 PSI!

      • Pancho

        Every product no matter how good has a life span. 17HMR was a huge financial success. On Midway right now 17HMR is more popular than Federal 230gr HydroShok’s and Golden Bear 7.62×39 123gr HP.

        • Dan

          22lr and 7.62x54r are still plodding along, more popular than ever.

  • Why is everyone complaining about “why?” or “another caliber?!” I say to hell with all of that, this is badass. If you can do it, why not?
    Do want.

  • Tinkerer

    Mh, according to the all-knowing Wikipedia, the H&K 4.6×30 in it’s 26 gr load, achieves 2380 ft/s of velocity and 330 ft·lbf of energy, while this new .17WSM with 25 gr load squeezes 2600 ft/s and 375 ft·lb. Oh the possibilities.

    • Dale

      Just what I was thinking. This round has a serious potential to function as a defense, hunting and plinking round. The only drawbacks that I see are the fact that it’s a rimfire cartridge (one of it’s greatest strengths for cost-effectiveness) and under-penetration with commercial loads. Either way, the terminal ballistics, cost effectiveness and limited recoil on this round will probably be ideal for an SBR or contender to the 5.7x28mm and 4.6x30mm platforms already fielded. I’m excited to see what happens with this cartridge and hope that someone develops a compact option, as well as an AR upper option.

      • noob

        The American-180 submachine gun could hold 275 rounds of .22lr in its biggest pan magazine.

        Discharging that magazine was demonstrated to destroy concrete blocks by the sheer number of projectiles hitting as they fired at the cyclic rate of 1200 rounds per minute.

        I wonder what kind of damage a rebarreled pre-ban full auto American-180 could do if each of the projectiles was a steel core AP .17WSM?

        and would anybody be crazy enough to consider it for the squad auto role?

        (in case of misfire on a badly primed rim you’d just pull the charging handle, like on every other squad auto.)

      • bbmg

        Noob, this is pretty much the idea behind the CBJ-MS:

        Smaller bullets but very fast and lots of them. I would favour the CBJ approach though because it achieves high velocity through the use of saboted bullets which means lower barrel pressures and less wear, and because it can be used with 9mm weapons which are a lot more common in police and military armouries than 22LR weapons.

        Using saboted rounds also gives you the option of using larger, heavier full bore projectiles fired at a lower velocity for when hard targets are not expected or for effective use with a suppressor.

      • noob


        The CBJ is an interesting weapon system, particularly the 100round drum magazine which seems incredibly compact.

        compare the 100 round 9mm glock Beta C-mag

        which is much larger, and that even counts what appears to be a taller feed tower.

        I hope that the CBJ gets wider distribution, rather than being strangled in its cradle by trade restrictions like the .224 BOZ

        which is again based on the 9mm case necked down.

        On the other hand… 100 rounds in the biggest practical magazine on a 9mm para case head size vs 200+ on the biggest pan magazine you could carry….

        I just want to see something that doesn’t weigh as much as a SAW make swiss cheese of automobile rims for fighting in an urban context where engagements are house to house and less than 200m

        the soviets knew the value of such a weapon in ww2 even without the barrier defeating projectiles when they outfitted entire infantry regiments with nothing but grenades and PPsh-41s.

        The AK series was an evolution (they even still call AKs “submachine guns” in some contexts) by going up in individual round lethality and penetration (within the technology of the day) but sacrificing how many loaded magazines you could reasonably carry around without encumbering yourself too much.

        Now that we have advanced powders and better AP projectiles (and deeply penetrative expanding projectiles for law enforcement and counterterrorism) we can get the lethality and penetration while also having crazy light weight.

        just the sort of thing you would want to storm stalingrad or fallujah with

        imagine a whole platoon that can lay down that much barrier busting fire for pennies a round?

      • bbmg

        The CBJ so far seems to have come to naught, which is a shame considering the apparent performance and the fact that converting your current 9mm weapons to the calibre sounds much cheaper than buying a whole new PDW system like the P90 or MP7.

        That being said I like the P90 for its groundbreaking configuration, it would be interesting to provide it with a similar tungsten slug in a nylon sabot to provide an even flatter trajectory and greater penetration.

        Interesting that you mention the PPsh-41 as the performance of the 7.62 Tokarev round it was chambered for is actually quite impressive. A test on the fantastic box-o-truth website shows it punching right through both sides of a kevlar helmet sitting on a water jug that even a 375 magnum couldn’t penetrate.

        For those who complain that these rounds are too small compared to a “proper” rifle cartridge like a 308, a look at any study about individual weapon effectiveness will show that the biggest issue isn’t bullets not causing enough damage, but actually hitting the target.

        A bad guy hit by one of these little rounds is infinitely more likely to be put out of action that one who is missed by hundreds of larger rounds. Throwing more fast rounds which produce less recoil downrange will invariably result in greater hit probability.

      • bbmg

        Something interesting:,436,175&ei=KszpULC5H6WG4AS-jYGoAw#v=onepage&q=2%2C436%2C175&f=false

        A 5 barrel 22LR submachinegun design for 22LR with a rate of fire of 3,000 rounds per minute. With a 50 round magazine that’s just a second on the trigger…

        This was patented more than half a century ago but so far it would seem nothing has come of it. The multiple barrels are there to take care of the heating issue, would be interesting to know if the lack of development of such weapons is due to technical reasons or the resistance to the use of a relatively weak round. It could be argued that the P90 and its ilk are a step in this direction.

      • noob


        the Neal looks exciting if pricey, and I’d want a five-shaft cleaning rod to speed up the cleaning process 🙂

        it would be exciting to build a semi-auto replica even if just for curio and relic purposes.

        And of course for hollywood. (the calico outfitted with fake rotating barrels in Deep Rising looks superficially similar)

    • John Doe

      How do the two cartridges compare when fired out of a barrel of the same length?

    • bbmg

      True, I would up the neck to fit a 22 bullet though.

      Under 300 yards you’re not going to notice much difference between 3,000 and 2,000 feet per second, and it’s always better to make a bigger hole 🙂

  • 511

    Can’t wait for this cartridge to come out, think about it, we would be getting a rimfire round that gets close to centerfire in performance at a price that won’t bankrupt you, especially with the ammo prices and severe shortages of today. I hope we see this chambered in a semi-auto platform. The versatility of this round is amazing, varmint hunting / self-defense / low-cost plinking / future zombie slaying (just kidding). Would be make a great revolver or handgun round too.

    I think the British dude in the comments below isn’t necessarily plugged into the U.S. gun culture so all this might be a bit foreign to him, that you would technically be able to have a highly potent hunting/self-defense round that would work both in a semi-auto rifle and handgun combo at a price point per round where one could afford to purchase thousands of rounds at a relatively decent enough price, and just in case carry a ton of it too. I’m willing to bet this is going to be a crazy popular round in California being that it circumvents a lot of the BS they have to put up with.

  • Michael Branson

    Winchester is advertising this cartridge has having the most case capacity ever for a rimfire and being the fastest rimfire cartridge ever. So if you want them to correct their ads to say “fastest rimfire cartridge not found in the oddball wilcat section of your grandfather’s old handloading manual”, you may start your email writing campaign to them now.

    • Reverend Clint

      *fastest and largest capacity currently massed produced

    • Clodboy

      I’d say the Henry rifle (known in the Civil War period as “that damned Yankee rifle that they load on Sunday and shoot all week!”) with its .44-caliber rimfire cartridge did play a pretty significant role in the history of firearms, so the .44 Henry isn’t exactly a completely obscure cartridge.

      But yeah, it seems nigh-impossible to find a rifle chambered in .44 Henry today, as even the Uberti copies of the Henry repeater are configured to fire .44-40 centerfire ammo.

  • Raoul O’Shaugnessy

    I’m predicting extraction issue of a high order….

    The problem with the .22 WMR was rather lengthy-for-caliber case having issues with sticking to the chamber walls. In an autoloader it seemed the only way to defeat this was to flute the chamber. This cartridge might not have as high a caliber/length ratio as the .22 WMR but I bet this thing is going to have some unforseen problem.

    On a side note, didnt Interdynamics experiment with a rimfire ‘assault rifle’ cartridge about 40-50 years ago that was kinda similar to this?

    • bbmg

      courtesy of

      “The Interdynamics MKR assault rifle was another unsuccessful and unconventional design of the Swedish company Interdynamics AB. Interdynamics MKR assault rifle appeared during 1980s on the top of the “micro-caliber” craze. The idea behind micro-caliber (less than 5 millimeters / .20 inch) ammunition was to achieve high velocity, flat trajectory and good penetration in automatic weapon, and with low recoil. The Interdynamics cartridge was based on .22 Winchester Magnum Rimfire cartridge case, with curved taper and 4.5mm / .177″ caliber pointed bullet, made of solid brass. Lightweight bullet (1.58 g / ~24.4 grain) achieved a muzzle velocity of about 1000 m/s (3270 fps). The effectiveness of this bullet was claimed to be on par with 5.56x45mm bullet at the ranges up to 300 meters. Unsurprisingly,the stopping power of such tiny bullet was questionable at its best, and use of rimmed, rimfire ammunition obviously compromised the reliability of the rifle.As a result,Interdynamics MKR assault rifle remained only in prototype stage.

      Because of the relatively low power of this ammunition, the MKR gun was made using simple blowback system. Rimmed ammunition was fed from semi-circular magazines, located behind the pistol grip, so the overall layout can be classified as bullpup. Ambidextrous charging handle was located at the top of the plastic receiver.Carbine version of the MKR rifle was similar in design, but had shorter barrel.”

  • Jeff

    The only concern I have is the COAL will not allow for chambering in current rimfire arms. That was the advantage the .17HMR had from dot. It is no longer than a .22WMR.
    Interesting innovation though. Good on them for the investment. For those that don’t handload yet another option.

  • noob

    At the risk of necro posting, have you noticed that tfb is running banner ads for the new misfire pistol


    Even from a short barrel, the fragmentation could be interesting.

  • carlhoffman

    Not much to say any new thing will have some appeal for me the 5mm Remington is back with ammo again being made. 12 ground hogs so far and none moved much after being hit.

  • Linden Mansfield

    I really like the sound of the .17wsm but am wondering if a .204 variant might be better, even though the 5mm Winchester rimfire failed, I really believe the WSM as a parent case would be a ball-tearing combination as a rimfire. I honestly believe the 5mm round failed only because of the preference for centerfires at that point in history, because of the perceived need for homeland defence chamberings. Now with the political climate favouring rimfire varminters, the door is wide open for a beautiful little pill spitter like the 5mmWSM*
    would be

  • Christine

    Too bad there is no cost-effectiveness with this round. Gougers buy them up and sell them for 3x retail. Hell, Gander Mountain, according to GunBot, is selling them for .36 per round! For that price you can get 5.56, 7.62 and .223!

  • wild bill

    The good ole “Hornet”,reloadable and economical will move a 40gr. spitzer faster. With 1 in 9 twist a 50gr. is very stabilized .Who needs this sure to be expensive rimfire???