Brice asks:

Why does a revolver need a .22 and .22 mag cylinder?  The Ruger Single Six, Taurus Tracker, etc all come with two cylinders.  Why?

Short answer is because otherwise the thing might explode. Here’s the long answer:

Two cartridges: .22 Long Rifle (LR) and .22 Winchester Magnum Rifle (WMR) (picture courtesy Wikipedia). On first glance these two cartridges appear almost identical in diameter, and all you would need to fire the WMR out of a LR chamber is to make it a little longer. But looks can be deceiving.

Let’s check out the technical specs of each of these cartridges (in inches):

Case Length.6131.055

Metric .22LR .22WMR
Bullet Diameter .222 .224
Neck Diameter .226 .242
Case Length .613 1.055
Rim Diameter .278 .294

You can see that there is a definite difference in size between the LR and the WMR cartridges other than just their length.

Bullet diameter doesn’t really concern us much, as the lead is soft enough to be extruded to the proper diameter for the bore by the expanding gasses without damaging any parts. The concerning part about these numbers is the difference in neck and rim diameter between the two cartridges.

Let’s imagine you try to fire a .22LR round out of a .22 WMR chamber. The cartridge will physically fit inside the chamber and the primer will more or less line up with the firing pin, so all seems well. But instead of the round fitting snugly into the chamber as it would if you had a WMR round in there the LR will be loose and rattle around more. That’s because there is more space between the brass case and the steel chamber than the designers anticipated.

The neck diameter on these .22 caliber cartridges indicates the diameter of the case from the neck to the rim because these are both “straight walled” cartridges where the sides of the case are parallel (much like a .45ACP and much UNlike a .50 BMG). That means that in a WMR chamber there’s .016 inches of extra space with a .22LR loaded versus the proper .22WMR round.

The effect of having too much space between the chamber and the brass case is pretty well understood. Too much space means the brass case can’t seal the chamber, and the result from pulling the trigger can often be more explosive (and firearm destroying) than intended. This is the best illustration of that point I could find, a perfectly good shotgun ruined because someone loaded a 20 gauge round instead of a 12 gauge round.

Here’s a slow motion look at a shotgun shell going off in an improperly sized barrel (or in this case no barrel at all).

Going back to our example improperly loaded firearm, once you pull the trigger the brass case of the .22LR round will expand to try and fill the much larger than anticipated chamber, most likely resulting in the case rupturing and splitting. Instead of all that energy being contained and directed forward, once the case ruptures the energy is free to impact the side of the chamber. More energy than normal is then directed outwards towards the wall of the chamber, and consequently the projectiles don’t go quite as far as they should. Because the case has split that means all of the force of the expanding gasses are applied directly to the chamber (instead of being retained by the brass case), and since the gases have had a moment to pick up speed before they impact the chamber wall that means that they’re moving faster and with more force than normal. The effect, as illustrated above, can rupture the chamber of a firearm.

In a low pressure round like the .22LR, this probably won’t cause the same catastrophic failure that we see in the shotgun, but it will definitely be bad for your gun and might possibly lead to some of the gasses escaping through the case head and fouling up the mechanism of your revolver. If your revolver’s chamber has been weakened (either by improper materials during manufacture or years of abuse) a kaBoom may indeed be in your future after all.

IN SHORT, you shouldn’t fire .22LR through a .22WMR chamber because the cases will rupture and you could ruin your gun, possibly exploding and killing everyone on the entire planet*. Ruger gives you a different cylinder for just this reason and I highly recommend you use it.


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*I said “possibly,” not “probably.”

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35 Responses to Ask Foghorn: Can you Fire .22LR Ammunition Through a .22 WMR Chamber?

  1. I dont really know about that, Nick.

    No, its not advisable… and I certainly would not try it for the safety of myself or my firearm, but I dont think it would be as catastrophic as you think. You have to remember that the WMR chambers are made to withstand higher pressures, and I dont think you would get enough pressure from the .22lr to rupture the chamber/gun. You might split some cases, and have piss poor performance from the round. However, I dont think that anyone would get hurt from it.

    I would also venture that with all the switch cylinder guns that are out there in existence there are probably a good many real world examples of this actually happening. I would bet that the anecdotal evidence would allow us to make a pretty definitive judgement on the matter.


  2. So if that’s all the situation, what’s the difference then with .357 and .38 revolver rounds? I hear about the two rounds being interchangeable in revolvers and folks firing them with no problems (other than a more/less sore hand).

    • Elliote, the difference is that the neck and rim diameter of a .38 special and a .357 magnum are the same. So, when the round is fired, the case cannot expand at all because it fits exactly into the chamber. However, you cannot fire .357 magnum out of a .38 special because the cylinder is not long enough to hold the longer round (which is quite intentional, because if you did, the higher pressure .357 will ka-boom your gun).

    • The 38 Special’s bullet is .357. So how did the “38” moniker arise?

      There were in the later part of the 19th century a large number of Civil War era Colt 1851 Navy cap and ball .36 caliber revolvers, obsoleted by the then new self contained cartridge.

      It was a simple conversion to drill out the cap and ball cylinder to accommodate a cartridge leaving the barrel bore unchanged at .36 caliber. The diameter of that new chamber, the OD of the cartridge itself, was .38 hence the name of the cartridge becoming “38 Short Colt.”

      From that beginning comes the subsequent evolutionary steps: 38 Long Colt (1875), 38 Special (1898), 357 Magnum (1934) and 357 Maximum (1983).

      • To put a finer point on it, the soft lead balls used in the old .36 colts were either .375 or .380 in diameter. When you load, a small amount is shaved off by the edge of the cylinder to give a good seal. When fired, they pass through a forcing cone at the near end of the barrel to reduce them to .36.
        And there was a lot more to the conversion than simply drilling our the cylinder. Look up Richards-Mason conversion.

        • Nope. You guys have it 180 degrees backwards.

          Original Navy Colt barrels had a 0.375 bore (grove) diameter and the first cartridges had to accommodate that bore.

          The reason the .38 special bullet is not .38″ is because the change-over cartridge (38 Short Colt) used a **heeled bullet** designed to fit the Navy’s, 0.375″ bore.

          Later, the 38 Long Colt and the 38 special after that, kept the 38 Short Colt’s case diameter of 0.381″ but abandoned the heeled bullet, reducing the bore diameter accordingly–hence the .357-inch “.38” was born.

          This holds true today–if you want to convert a reproduction Navy cap-n-ball to shoot .38 special, you will get your best accuracy using heeled bullets (ie, .375 caliber bullets). There are ready-made “conversion” reproductions that are proper .38 specials, but these are made entirely for the convenience of the modern shooter.

  3. The 357/38 cases are the same diameter-same with the 44 Special/44 Magnum,and therefore the subloads are safe.
    In the Ruger SP101 in 327 Federal Magnum it is safe to also fire 32 H&R Magnum;32 S&W Long;and 32 S&W.There could be carbon ring issues with the latter two.
    It is safe to fire 22WRF in a 22 WMR chamber also,although there isn’t much 22 WRF around nowadays.

      • 1) insert a 22lr in a 22wmr chamber
        2) pull the trigger
        3) no bang, no kaboom, no nothing
        4) eject the fired 22 lr case
        5) now this is the best part: DO NOT LOOK for barrel obstruction
        6) go on and insert a 22mag round in the 22mag barrel
        7) pull the trigger
        6) kaboom!!

        • That’s something that you should do whenever you get a click and then extract a spent case, we’re talking about improper ammunition use today which is a different issue.

        • I have intentionally chambered a 22 lr in a 22 wmr rifle.- ( a cz 452), following a
          discussion with a friend of mine.-
          It was a standard velocity round.-
          The rifle fired and I estracted the case.-
          The case was not ruptured, but was expanded, there was some unburned powder on the bolt face.-
          The bullet was lodged in the barrel , 10 inches from the chamber.-
          I am talking about improper use of
          ammunition,and, in my opinion, this
          is a very dangerous situation.-

  4. Thanks for the answer. I didn’t realize the 22mag was that much different. I ass u me d. That because the barrel was the same, the bullet would bathe same.

  5. Here’s all the specs anyone might want on .22 rimfire ammo:

    NB that the SAAMI spec chamber pressure for the .22LR and .22 WMR are the same (24 kPSI), but the WMR tested lots showed higher sampled mean pressures by about 3K psi.

    Probable result of a .22LR in a .22WMR chamber will be case splitting and gas excursion out of the chamber. In a semi-auto, there might be a problem with extraction. Since the .22LR is smaller in diameter than the .22 WMR pill, accuracy of .22LR rounds put through a gun with a .224 barrel will be less than optimal, even when you have the correct cylinder.

    Re-chambering a .22LR for .22 WMR is right out.

    To give people a relative frame of reference, chamber pressures for high power rifle rounds are anywhere from 48 kPSI to over 60 kPSI. Above 70 kPSI, one should start to worry about case failure, even with proper headspace, with attending “bad things” happening. .22’s are, relatively speaking, low in pressure, but not as low as shotgun rounds, which range from 11 kPSI up to somewhere between 15 to 16 kPSI for a pretty warm shell load.

    As for barrel failure: Most .22’s have far more steel around the chamber than they need. I’d want to see someone blow up a .22 barrel before I’d predict that it would happen.

  6. The photo of the exploded 12 ga O/U shotgun I’d guess shows what happens when a 20 ga shell is loaded, which then slides forward too far in for the firing pin to strike, unfortunately still leaving room for a 12 ga shell to chamber behind it. Subsequently the 12 ga shell fires into the jammed in 20 ga shell causing a major KA-BOOM.

  7. There are two major points that this article gets wrong:

    First, you will not blow up a 22WMR by shooting a 22LR. You’ll foul the chamber, errode the throats, get terrible accuracy and probably end up extracting a lot of split cases…but that’s all. It’s not good for the gun but it’s not a kaboom waiting to happen either (lord knows I’ve done it enough)

    Second, you cannot fire a 20gauge shell in a 12 gauge gun–the 20 gauge shell will not chamber, I’ll just slide into the forcing cone. That kaboom was the result of someone dropping a 20 gauge shell into a 12 gauge gun and THEN (somehow) dropping a 12 gauge shell in after it (read more here:

  8. Ok, I just went out and did this after reading. I loaded a 22lr in my 22 magnum S&w 51. You know what happened? It went bang. The bullet hit the target. I wouldn’t do it on a regular basis, but nothing bad happened. Nothing.

  9. I too have done this unintentionally in a Ruger Single-six. My Grandpa was missing one of his 2 cylinders for the gun, and I was sure that the Magnum cylinders were left unfluted to differentiate them from the LR. The cylinder in the gun was fluted, so I loaded up a couple cylinders of LR and couldn’t understand the crummy accuracy I was getting. As Daver said, I got bulged, sooty cases, some with a split, and crummy accuracy. I think the article paints too dire a picture, but no, it still isn’t a good idea.

  10. Recommended purchase and required reading: “Cartridges of the World-11th Editon”, by Frank C. Barnes and Stan Skinner. Everything you want and need to know about modern or obsolete rifle, pistol, and some shotgun cartridges.

  11. Unless I miss my guess, the blown 12-gauge shotgun was destroyed because someone loaded a 20-gauge shell then loaded a 12-gauge shell behind it and tried to fire the gun. The NRA Firearms Fact Book cites this sort of barrel obstruction as one of the most common with shotguns, the relatively large mass of the 20-gauge shell (compared to the typical shot load) creating the damage. (Also possible that the 20 gauge shell might go off creating a bigger problem.) But characterizing the picture above as an example of loading a “20 gauge round instead of a 12 gauge round” is misleading. More accurately, it’s the result of loading a 20 gauge shell AND a 12 gauge shell – at the same time!

    As for all the theorizing about brass ruptures and cylinder diameters – color me dubious. The variation is .008″ variation in radius. Case wall thickness for a 22LR is approximately .010″. Let’s assume that the case wall didn’t simply expand, but rather sheered completely. In that case, there would still be .002″ sealing the shear rupture. Remember, brass under pressure flows. Lots of wildcat loaders (or owners of firearms with obscure calibers) “blow out” other cases to match dimensions in the target caliber. Without looking, I’d assume a LOT of those are more than .016″ expanded.

    Note in the shotgun shell video that the powder does not ignite (pretty clear at the 00:05 point). Not sure what relevance the video is supposed to have to the article. (Primers alone aren’t generally responsible for catastrophic gun failures).

    The bit about gases “pick[ing] up speed before they impact the chamber wall … moving faster and with more force than normal” appears to be related to the rupture that likely would not occur… and I don’t really buy it.

    My bet is that dual cylinders are a matter related to accuracy more than safety.

    I’ve seen some good “Ask Foghorn” articles. This wasn’t one of them.

  12. has anyone tried a 45 colt in a 410 ga. shotgun , I did as it was marked as OK to shoot , but what happened was the brass coat of the 45 colt bullet pealed off in the chamber, so you may be ok with a total lead bullet , but watch out for bullets with soft brass jackets… I shoot 38 special lots in my 357 mag . guns never had any problems, also tried 380 auto in my Marlin 9mm camp carbine fires ok , but leaves lead in chamber…and one time fired 7mm Rem. in my 7mm Mauser fired ok but brass could not be reloaded as was fire formed and too short… have fired 22 CB and 22 short and long in my 22 long rifles , some brass does not come out easy, others do ??

  13. WOW. You are usually very knowledgeable and I respect your writings but not this time?? I do agree completely that the proper ammo should always be used in any gun and using the wrong ammo can sometimes lead to extremely dangerous or fatal situations but there is little danger in firing .22RF in a .22 mag chamber. The only victim is usually accuracy. The convertible revolvers usually have a compromise bore dia of .223. For starters, your example of the 20GA fired in the 12GA isn’t even possible. Yes accidentally putting a 20Ga shell in a 12 ga has blown up many a 12 ga shotgun but not by being fired! They slip right down out of sight in the 12Ga chamber and the rim jams solid in the forcing cone with plenty of room to load a full 12Ga shell on top of the 20Ga shell. The 20Ga can’t be fired there unless you have a firing pin that reaches all the way to the forcing cone?? The gun blows up when the stuck 20 ga shell is undetected and a 12 ga shell is loaded on top of the stuck 20 Ga that is effectively blocking the bore. Extremely dangerous to the shooter and anyone standing near by.
    The expanded cartridge case is indeed the seal that prevents gasses from traveling backwards into the action and possibly into the face of the shooter with serious consequences. The chamber wall supports the brass. Not the other way around. The thin brass case cannot possibly support a weak chamber wall. A split case has little effect on the pressure on the chamber wall. Split cases happen often and don’t blow up chambers or barrels. Think of full load fire forming?? The chamber wall supports the brass. If the chamber wall is weak, the thin brass isn’t going to help it much. Both .22 RF and .22Mag cartridges are rated at the same 24,000 PSI rating. A .22 is a smaller case firing into a larger chamber thus the pressure will be lower, not higher if the case splits or not. Firing a .22 RF in a .22 mag gun is more of a feeding issue and accuracy issue than a safety concern. That of course doesn’t apply to other calibers where there may be a great concern of damage or death by using the wrong ammo.
    I hate to contradict you because you usually offer excellent advise. Just not this time.

  14. Go ahead and put .22lr in .22wmr. done it hundreds of times, no danger. seems that there are some pretty meek gun owners out there. better trade for an air rifle.

  15. With all the conflicting information regarding the .22, I believe I will stick with what some posts have said: I will use the appropriate ammo with the appropriate cylinder. I believe it will be safer for the weapon and myself. If I get criticized for this view, so be it.

  16. I would like to inject a bit of reality here. Most posts don’t indicate personal experience.
    A friend brought his Marlin 15Y 22 mag to the range. He was firing 22 LR in it for quite a bit. I noticed the swollen cases and checked the barrel markings. sure enough, 22 LR in a 22 MAG. No explosion, no split cases, nothing unusual at all. Even decent accuracy. He’s had it for years and never used anything except 22 LR.
    We corrected him, warned him to clean it out and check for a carbon build up. After cleaning no problems were noted.
    I just watched a video on where a Little Badger in 22 MAG was repeatedly fired with 22 LR with no problems. He did point out the swollen cases but no problems came up. I suspect that the company uses a 22 LR blank for both calibers. Cost point almost demands it.
    I just got my Marlin 982S 22 MAG bolt action, clip fed rifle out and checked. It will cycle 22 LR & shorts. Even mixed magazine fills. I will take it to the range and try it for myself. I expect it to work fine. I suspect accuracy will be average at best. Marlin probably used a 22 MAG blank because it is a more expensive rifle.
    I like to make my own informed decisions based on best advice, logic & safe testing.
    I reload “NONRELOADABLE” steel (Wolf) and aluminum (Blazer) cases. If they have a single flash hole, I reload them. I carefully tried the 45 ACP cases in a Ruger New Model Blackhawk because of its strength. Aluminum reloads once. Steel reloads 3 times.
    I also had a container to store all the powders I didn’t mark properly for later disposal. I mixed it 50-50 with Bullseye and loaded up some midrange 38 SPL rounds using Bullseye data. I reasoned that Bullseye is the fastest powder I use, so it should be fine. It worked great. I fired the loads in a 357 just to be safe. I was able to reload 38 SPL in the middle of the ammo drought.
    Do I recommend you trying it? NO! My guns, my components & me trying it out. Was it unsafe? I don’t think so. But I have reloaded for 40 years and I reload for over 50 calibers. I’ve had to come up with loads for obsolete calibers and make my own cases out of available brass.
    Now, having said all that: use the right ammo and be safe.
    P.S. I am also an NRA Certified Instructor and I teach use the right ammo!

  17. I have an H&R 12″ barrel 22/22mag revolver w/ two cylinders. I forgot I had the 22 mag in one day and shot a few loads of 22 LR. I kept saying to myself, why is the accuracy so bad? Then I realized the mistake and switched cylinders. I didn’t notice any spllit cases or anything else. I have been considering boring out my little Rossi single break open (has also a 410 barrel) for 22 mag. I think it might be ok for a break open, but not for any other 22 LR

  18. On a north american arms derringer chambered for .22 wmr it wouldn’t matter. The barrel is so short so the .22 lr bullet doesn’t get stuck, the .22 lr case ruptures but the pressure isn’t enough to do anything to the revolver since it is meant to handle the .22 wmr and the airgap between the barrel and cylinder also vents out some pressure. But then again why would you load a .22 lr on a gun that is designed as a backup gun? Its not like you are going to do any target shooting or plinking with it.

    • My only experience with this issue was using .22LR in my Davis Derringer, which is .22 magnum. It seemed pretty safe, but I did use a heavy welding glove the first dozen or so shots, just in case.

      This was a rather odd use, of course. We were preparing for a Retriever Field Trial and needed to make a lot of pigeons dead so they could be planted as blinds (rather than released & shot). I refuse to do the usual neck-twist, by holding the head & twirling the bird’s body around four or five times, after I found several of the birds STILL ALIVE in the bucket 8 hours later. Pigeons may be flying rats … but I won’t cause that kind of distress to any critter, sorry! So I used my little Davis Derringer & some .22LR ammo I had in the trunk, and dispatched thirty or so pigeons by popping them in the head. Clean, humane, worked fine. And I had NO trouble with sticking cases or ruptured cases. The .22 LRs ejected normally. I did this several times over several hunting tests, and must have run close to a hundred .22LRs thru it without issue.

      Now, I know that the Davis Derringer is supposedly a cheap little thing, just a belly gun made out of rather weak pot metal, and is probably NOT the ideal weapon to try this in. Now that I know about case diameter differences, I would hesitate before trying this again.

      That said, I suspect that in a decent-quality .22magnum firearm, the odds of a serious problem are probably remote — leaving aside the separate issue of semi-auto feeding & ejecting properly. I won’t risk my nice Grendel .22 magnum pistol to experiment with this.

      However, my advice to other gunners is going to be DON’T DO IT, unless for some odd reason your life depends on it. With guns, there is no such thing as “too safe.”

      I still love that cheap POS Davis Derringer. It cost me $34 wholesale 25+ yrs ago when I had an FFL, so I bought three of them, two still in the box for my son. Unlike my Rugers & Smiths, it’s ALWAYS in my pocket, even if I’m just going down to our pond to fish, wearing only a pair of shorts & a hat, or walking down to the mailbox. It goes in my pocket along with change & keys every morning & stays there all day, and since there is no fine finish left, just scratched gray metal … who cares if it gets more scarred, or covered with fish guts, or gets wet when I wade in to unsnag a lure? The best defense gun is the one that’s always with you, even if it is a tiny, cheap POS. And it’s a decent backup piece when I “go formal” and carry a .357 or .38.

  19. Both the 22LR and the 22 mag, have a .223 bullet the 22LR has a trimmed end where it goes in the case, the case is the same size as the bullet. The 22 Mag is inserted in the case, the case then is larger then the 22LR. Once the 22 Mag is fired you can stick a 22LR down inside the 22 Mag, that is because the 22LR case ans all is the same size as the bullet, Do some measuring for your self, you will see this is correct

  20. The .002″ of diameter is not very significant, and it’s unlikely that you will blow any chunks out of a cylinder with a .22LR in a .22WM revolver. With the extra slop, you will not obtain consistent accuracy, and that is just wasting your .22lR ammo, and slowly tearing up your .22WMR pistol, regardless of the action or type of gun. You are putting more fire and hot gas in places it really does not need to be. This is going to erode the chambers in the cylinder slowly, and make the whole gun prematurely sloppy over time. Let’s look at 22WMR autolaoaders. Many of these are delayed blowback actions specifically made for .22WMR. Changing the pressures and having gas leakage is really asking for trouble. The same can be said for recoil or gas operated mechanisms. Those are timed using springs and gas regulation set up for the .22WMR, not the .22LR, with leakage. Bolt & lever guns, are in the same boat as the revolver. You are just putting unnecessary wear and tear on the chamber, for no good reason. I have fired .22 short and .22LR from pieces of car antennas, stuffed inside steel tubing. It’s called a “zip gun”. We used the ball and final steel rod of the car antenna as a firing pin. DO NOT TRY THIS AT HOME, OR ANYWHERE ELSE! I have seen those blow up. It’s not pretty. It generally never happens the first time you use the gun, so you stop wearing the welding gloves, and wind up with a mangled finger or hand. I am lucky to be alive, let alone still have both eyes, all my thumbs, fingers and toes still in tact. Hair grows back. My hearing is definitely not so good anymore, and my sanity is still being debated.

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