Sorry, I have to start a gun thread. Only to call out lunatics.

[spin]

16. The S&W lock was a simple device that offered some advantage to certain handgun owners. ...

Perhaps it should have been offered as an accessory but installing it on all new S&W revolvers was a marketing disaster. Another factor which hurt sales of S&W revolvers with the lock was reports of the lock spontaneous locking. This actually happened to a shooter on a pistol range I was at and since I had a key on my keychain, I was able to unlock his firearm. I own several revolvers with this lock and have had no issues with them.

INTERNAL GUN LOCKS

Massad Ayoob
Thursday, September 3rd, 2009

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&’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.

***snip***

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.

***snip***

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.)

***snip***

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.(...emphasis added)
http://backwoodshome.com/blogs/MassadAyoob/2009/09/03/internal-gun-locks/