I am a proponent of carrying smaller calibers in pocket pistols. Specifically, I really like mouse guns in 22LR, 22WMR, and 32ACP; trading "stopping power" for capacity and improvements in shooting characteristics. One of the biggest concerns I see when discussing rounds like 32ACP or 22LR for defense is the potential for rim lock. Curious how much problematic these rounds can be, I set out to answer the question myself. Is rim lock a serious issue, or just an overblown concern?
What Is Rim Lock?
Rim lock is an issue almost exclusively found in box magazine fed firearms, both autoloading and manually repeating in nature. This occurs when the rim of a case gets trapped behind the rim of a following round inside the magazine. The lower round's rim prevents the forward movement of the round attempting to be fed, often resulting in a challenging stoppage. These stoppages often cannot be cleared with a typical "tap and rack." This can occur if rounds are jostled in the magazine under recoil, but is more commonly attributed to improper loading of the magazine. Traditionally, rim lock is not a concern with tubular magazines, as it is nearly impossible for rims of different cases to interact with each other.
Now that we know what rim lock is, let's look at how often it happens.
How Common Is It?
As someone with relatively limited experience with 32ACP and a fair bit with 22LR, but no examples of this happening personally, I was curious how much of a problem rim lock really is. To help answer this question, I enlisted the help of several friends and colleagues. Some of these people include Greg Ellifritz, Chris Baker, Darryl Bolke, Bryan Eastridge, our own Paul, and several others. Initially, I narrowed our criteria to 32ACP, as that round is more digestible for personal protection for some than other rimmed rounds. Over 30 different firearms were used, to include the Walther PP, KelTec P32, Beretta 81 and 3032, and a variety of surplus pistols.
Across thirteen shooters, and over 13,000 combined rounds of 32ACP fired, the results were shocking. On the low end, we have five confirmed cases of rim lock. On the high end, foggy memories could be has high as 10 total cases of rim lock. That's somewhere between 0.0003% and 0.0007% of rounds fired resulting in rim lock. Two of these examples occurred with the KelTec P32, one of which was documented in a video from The Suited Shootist. The three other confirmed examples were with the Beretta 81 when paired with aftermarket magazines. Interestingly, zero cases came from antique pistols such as the Colt 1903, Browning 1910, or Frommer Stop.
Analyzing The Data on Rim Lock
This shows us two things. One, rim lock is a real thing that happens, even to very high level shooters. Two, the likelihood of rim lock occurring is astronomically low, and I believe, overblown, when it comes to 32ACP pistols.
If rim lock were to occur in the middle of a defensive encounter, the results could be catastrophic. Taking this into consideration when choosing your tools for personal protection is critical, and only you can decide if the risk is worth the reward. After doing my own vetting with my guns, I would take that bet everyday, and do so from time to time. Rim lock is only one factor in reliability, and is likely something you'll work through when doing your own evaluations.
Rimfire Rim Lock
32ACP isn't the only rimmed cartridge used for personal protection in autoloading firearms. Some may consider it unfit for even the smallest game, but the ubiquitous 22LR is a better choice than often given credit. There are even a handful of 22WMR automatics, though their popularity is dwarfed by its smaller brother. However, this is not a piece on the justification of rimfire rounds for personal defense. That discussion is for another time.
Much like the larger 32ACP, rimfire rim lock really doesn't happen that often. To that end, the results are even more stark considering how many more rounds of 22LR people shoot versus 32ACP. Across roughly a dozen shooters, we have well over 30,000 rounds of 22LR recorded between us. Guns tested include the Taurus Tx22, Ruger Mk series, Lite Rack, SR22, the KelTec P17, Beretta 21A, and more. Not one case of rim lock to be found.
Zero examples despite an incredible diversity of pistols, and the wide variety of quality in 22LR ammunition. Even with my own experiences, the results still surprise me.
Final Thoughts on Rim Lock in Pistols
Even before gathering this information, I wasn't terribly concerned with rim lock. Now that I've seen the numbers, it's really only slightly more common than being struck by lightning. Again, this isn't to say that rim lock never happens. However, it does seem to be incredibly rare, especially as you improve the quality of your guns and ammunition. If this is the one concern holding you back from carrying a rimmed cartridge, hopefully this provides some relief.
Rim lock is something to consider, but not something to fear.
Author's Note: This isn't a commentary on the overall reliability of these gun and ammunition combinations, as there are too many variables at play to discuss here. Nor is this an endorsement by anyone who took part in my data gathering of anything said here. If you want the opinions of those who assisted, reach out to them, most are very responsive. Additionally, I appreciate their hard work and willingness to provide their data. They've helped increase my confidence in my selections, and this piece would be diminished without them.