Earlier blog posts on new Smith & Wesson products here in the last few weeks triggered a visceral storm of criticism in the Comments sections for S&W’s continued installation of an internal lock on most of their revolvers. The turn of the key locks the mechanism and renders the gun unshootable, even if it is fully loaded.

S&W has departed from the current policy twice. First, as mentioned here in comments, they quickly sold out a run of Airweight .38 revolvers made on older frames in stock, which did not have the controversial feature. Second, they’ve had good sales of their “lemon-squeezer” series, so called because these models come with a grip safety that the company feels, apparently, makes the internal lock redundant. These are still available, and can now be had in Airweight, the Model 42-1.

My experience and research has shown that spontaneous locking of the guns during firing (characterized as an ILF, or Internal Lock Failure) has occurred, but rarely. It normally involves very powerful guns with very violent recoil, and also very light guns (Scandium, Titanium) firing these extremely hot rounds. The buffeting from the heavy “kick” seems to be what’s jarring the parts out of alignment.  However, one of our readers reported in the comments section that he saw an all-steel S&W spontaneously lock after it was accidentally dropped. Again, a violent impact to small parts seems to have been the culprit.

I know several folks at Smith & Wesson, some highly placed, who don’t much like the locks either. However, prevailing corporate policy says the locks are going to stay for now.

Personally, all the S&W revolvers I carry or use for anything serious are older models without the locks. While I’ve bought several of the lock-equipped later models, all but one were for sport. The single exception is the Model 340 Military & Police, a roughly 14-ounce five-shot pocket revolver chambered for .357 Magnum. This gun has a unique sight concept: a huge XS Tritium Big Dot front, and a humongous U-notch rear.  Developed by S&W engineer Jason Dubois to the best of my knowledge, this arrangement allows the very rare combination of fast sight acquisition in poor light, AND extreme accuracy. This gun puts every shot in one hole at 7 yards if I do my part. I’ve shot hell out of it with hot .357 Magnum loads and never had a spontaneous lock, but I still carry it with milder 135 grain Speer Gold Dot 135 grain +P .38 Special just to be sure. (And because, in a gun this light, the Magnum rounds are just painful to shoot.)

I did not remove the internal lock, for the simple reason that I’ve seen a prosecutor raise hell about a deactivated safety device when trying to establish the element of recklessness that is a key ingredient in a manslaughter conviction. “Ladies and gentlemen of the jury, the defendant was so reckless that he DEACTIVATED A SAFETY DEVICE ON A LETHAL WEAPON, and so arrogant that he thought he knew more about the gun than the factory that made it!”  That’s a mountain I’d rather not have to climb in court, nor debate in front of twelve jurors selected in part by opposing counsel for their lack of knowledge of firearms.

Smith & Wesson makes their Military & Police semiautomatic pistol line with options: the customer can have it with or without manual thumb safety, and with or without internal magazine disconnector safety. I wish S&W would offer the same options with their revolvers, but it’s a much more complicated and expensive thing to do in revolver as opposed to pistol manufacture.  In the meantime, we simply have the choice to buy a different brand. If you have chosen to remove the internal lock feature from your late-model S&W revolver, do yourself a favor and download copies of threads on gun forums in which this issue is discussed, and cases of lock failure are documented.  Keep them on file. If you become the test case, that material may help to defuse arguments that removing THIS particular safety device means you’re a reckless person.

When the sights allow a five-shot group that all hit the aiming paster at 7 yards like this, without even using the Crimson Trace Laser Grip’s projected red aiming dot, Mas can forgive the internal lock. Keyway is seen above cylinder latch on this Model 340 M&P .357.



  1. S&W does not make new 642’s w/o the IL, they’re just older frames they have that are released.

  2. Bought a new 642-2. Shot 50 rds first day ,no problem. Played witn internal lock and key, turned on and off etc. Second day shot 8 rds, cylinder locked up, would not shoot. Unloaded it, then spun the cylinder and it started working, shot 2 rd , locked up again. Asked my wife to shoot it to make sure it was not me. Dry fired it ,worked fine. She loaded it up and fired 2 rds then quit working again. Have lost faith SW. Probably I will not call SW, just fix the problem myself, What a deal! If I had know all the problems with ILS would not have bought SW.

  3. I was disturbed to discover that a Ruger LC9 that I had ordered has an internal lock on it.

    Does anybody know of any problems with that weapon caused by the lock and whether (and how) it can be modified to disable the lock without adversely affecting the weapon’s functioning?

  4. I have a 460 with a lock. does the 460 have one key fits all or does each model have a key or is there a key for each serial number. And how do I get another one I lost mine but would like to get the key replaced just in case.

  5. So.. I just came across this blog post, while looking into why my S&W 642 my wife got me for V-Day wont unlock!
    Bought on friday, ran 35round in it Sunday. Took home, was going to clean. Figured i would engage the lock, just to see if cylinder lockd as well.. You know just to check out!
    Well after engage’n the lock, i cut it back off. Now its lockd no matter what way ya turn key! So guess in calling the factory tomaro! Very unpleased!! Even more this was goibg to be my backup! Now it will be sold when i get back, or just made a range gun!

  6. I was lucky enough to get a new 642 (no lock) a few months ago. I refuse to get one of the locker models. I hit a few gun shops in my area or do a legal internet transaction to get an older S&W to add to my acumination. Got to admit there seems to be a lot like me as it’s getting harder to find those guns for sale.

  7. My 642 with lock has had the gun lock up TWICE during firing at the range .

    Sent the gun to S&W twice. Theyh said they test fired 50 rounds with no problems and sent it back to me.

    Jerry Miculek said maybe while firing a lot of LSWC bullets they caused the cyl. face to drag on the rear bbl. face. Due to lead fouling. Then the hand couldn’t rotate the cyl. locking the gun up. This happened while firing the usual 50 practice shots

  8. Since S&W is offering the 642 now without the lock, it would seem that removing the lock plate in those with an IL could be considered and upgrade or improvements (as luangtom suggested).

  9. I own one S&W revolver with the IL, a 657 bought with the specific intention of being a deer hunting gun. The first time it locked up, I sent it back to S&W for “repair”. They said they didn’t have a problem with it. The second time it locked up, after about 75 rounds total, I had my friendly gunsmith permanantly resolve the problem. I normally have the concept that any and all of my guns should be reliable for use a defense tools should the need arise. The 657 broke that mold; it’s about the 15th S&W revolver I’ve bought. No more with the locks. The 657 does great in its current state, and is very accurate to boot!

  10. Last week I bought a new S&W M&P 340 without the internal lock. I knew if I waited S&W would make it without the lock. Couldn’t be any happier. Excellent results with the Gold Dot 38 special + P 135 grain short barrel ammo. This is fast becoming one of my favorite weapons. Maybe the perfect all around CCW weapon for a non LEO. Perfect BUG for an LEO. I did order Crimson Trace Laser grips from S&W.

  11. I purchased a new, S&W 638CT in June 2015. Shortly after taking possession, I was at home practicing opening and closing the cylinder of the gun, without loading or firing it. I opened and closed the cylinder a number of times, when all of a sudden, after closing the unloaded cylinder, the gun locked up. I unlocked the gun and continued to practice opening and closing the unloaded cylinder, when suddenly it happened again; upon closing the unloaded cylinder, the gun locked up. I had not heard of any problem with the locking mechanism before I purchased, but after having this problem, I went on line and found out that the lock problem is widespread and has been known for years.

    At that point, I put the gun back in the box and emailed S&W Customer Service. S&W Customer Service replied with the statement “We have received your email regarding your firearm. We would suggest returning the product for our examination.” They authorized me to send the gun back and sent me a shipping label and directions for shipping.

    I sent the gun back on July 2, 2015, and included a letter telling S&W the following: “I need S&W to fix this problem with the internal lock mechanism in my revolver, under warranty, at no cost to me, so that the revolver’s lock system cannot ever again inadvertently lock the mechanism on its own, without a key. I need S&W to make sure that the lock will never again engage unless I purposely use the key. If this cannot be fixed, I need S&W to replace this revolver with a similar model that does not have the internal lock mechanism, and I would expect this replacement to be done under warranty and at no cost to me.”

    I will try to report back to this website what I find out from S&W and if they fix this problem for me under warranty.

  12. So, you are willing to believe a disabled internal lock, or reloaded SD ammo, will make a case go from justifiable homicide to murder even though you cannot cite a single case of that actually happening yet are inclined to believe that the internal lock is fine since it only rarely causes a problem even though it is well documented that it does, in fact, lock up on its own and you even admit you do not want them for serious work. Either refuse to buy an IL S&W or don’t, you cannot have it both ways just because you like S&W, the company has changed and needs either a new spine or to go out of business.

  13. Bought a (used, wonder why it was re-sold?) S&W Stainless airweight snub with internal lock. Used it at the range a couple of times and it “locked up”! I returned it to the dealer and he tried to tell me I probably did not close the cylinder. I like wheel guns and have been shooting them for 60 years. Never failed to close a cylinder. First thing I checked when It did not work. Traded it in for an “old” model 36 which I have now fired a couple thousand times with no lock up or my failure to close the cylinder. Absolutely no more internal locks for me, my wife and I are too precious to carry one.

  14. I only own one S&W with the dreaded lock and will not be buying another. If you remove the sideplate and actually see how it works it is incredibly flawed and seems like it could have been designed better. S&W should be ashamed to be selling people such nice looking revolvers with a lock that is not 100% fool proof. It is no wonder so many have “locked up” while in use. But there is good news. There is a user on the S&W forum that has been making plugs. He sells them for every frame size and in either stainless or blue. Get one. They work. I got one for mine and it’s the only reason I decided to keep the revolver. But from here on out it’s older Smith’s for me. Pre-lock and pre-MIM triggers.

  15. Just got a 642-2 because it meets my needs… have locks that I never use on a Bersa Thunder (.380) And a Taurus 85 (.22), and both work perfectly after many rounds on the range. After looking at the lock on the 642-2, I can imagine why there are problems, I don’t have time to find an older model without the lock so I will have to think of a fix…. I appreciate all the thoughts about solving the problem it saves me a lot of time.

  16. I have a 20 year old 686+ with no lock that I love. It would likely be the last of my guns to get rid of, which is to say, I’d never get rid of it. For me the lock’s biggest drawback is that it takes away from the best looking revolvers made, It’s ugly and superfluous. I keep waiting for Smith to do away with it and they never do. They don’t seem to realize that they’d see a huge spike in sales from guys like me if they were to bag it. I do have a 642 with the lock and want to tell all of you who hate it that it’s a snap to disable. Remove the side plate, the main spring and the hammer and it’s right there. Just take it out and no more IL. The only drawback is that removing it leaves a hole on the side plate, which could allow dirt and other grime to get in there. Other than that it’s worth it in a defensive firearm.

  17. Bought a 638 a short time ago with no regrets. I did remove the lock piece and kept it with both keys set aside in my gun case. If I ever sell the gun or need to return to S&W I will put the lock piece back in the gun.

    Have carried my M49 for number of years and decided to get a lighter carry piece and this fits the bill. I see nothing wrong in removing the lock piece and see nothing to take away from its appearance. I bought for self defense and not a show piece. Come on now and get real. A little hole does not take away from a good carry piece.

    I think S&W should include a key hole plug in the kit for cosmetic reasons if anyone is that sensitive.

  18. Simple solution since SW still have locks everywhere is don’t buy a SW.
    Literally dozens of nice pistols out there and if you want a revolver, buy a Ruger. Maybe one day the pistol angels will bring colt back from the dead. Till then show SW they don’t deserve your cash.

  19. I would never buy a Smith with the lock. It’s ugly, completely unnecessary, and a dust magnet, and introduces potential failure. Plus it just stands out like a sore thumb and looks cheap. I can’t ever bring myself to buy a new Smith with a lock, much as I like S&W. Sad.

  20. The M&P340 I posted about here in 2012 is still pocket carried, in a holster, daily. I’ve been through a variety of three eightys, settling on an LCP, but it is only carried when deep concealment is necessary. I carry the short barrel Speer +P 135 grain HP b/c most of the .357 loads are too hot for quick follow up shots.