The issue of the internal lock that S&W added to their revolvers is one that has generated far more heat than light on the internet over the last several years. Initial resistance was mostly split along two lines: The first was aesthetic; the new lock appeared as an ugly little metal zit on the side of the gun just above the cylinder release, complete with an inscribed "L"-and-arrow indicating which direction to turn it to disable the gun, and a Rube Golberg-esque flag that popped up to indicate that the gun was locked. The second was philosophical; people refused to buy a gun that had a feature that was such an obvious nod to the anti-gun crowd and could render a sidearm inert at a time when it was needed most.
The issue was complicated when, after a year or so, rumors began to trickle down about revolvers that had spontaneously locked themselves when firing. Several prominent gun writers pooh-poohed these claims in print, predictably resulting in incendiary internet diatribes about "paid shills of the gun industry". The argument has smoldered fitfully along ever since.
Recently a thread on ARFcom, complete with pictures, concerning yet another spontaneously-locked revolver has triggered yet another flareup of "See? I told you so!" on the web, including posts from people on Evil Black Rifle gun boards who are no more likely to carry a S&W revolver than they are to sprout wings and fly.
As usual, the truth about the matter lies somewhere in the middle, and I'd like to offer a couple of thoughts on the matter. Remember, I'm just someone who worked in the retail firearms sales and repair industry from 1993 to 2007 and who has owned probably close to a hundred S&W revolvers, including three with the dreaded internal lock. My opinions are no more valid than anyone else with a keyboard and an internet connection:
1: Locks are not some demonic S&W invention. Springfield, Bersa, H&K, Glock, Taurus, Ruger, and S&W all have locks on some or all of their handgun lines. These locks are all done with varying degrees of mechanical aptitude and aesthetic obtrusiveness. Barring a significant change in the American political and legal climate, locks on handguns are with us to stay. A ban on handguns is more realistically likely than the disappearance of integral locks. Deal with it.
2: S&W are not the only locks that have failed. Over the years I have seen one failed S&W lock with my own eyes. I have also seen one Bersa, one HK USP9F, and a double handful of Tauruses that have suffered some manner of lock-related failure that rendered the gun inoperable.
3: Verifiable S&W lock failures seem confined to a narrow class of firearms. Almost to an incident, they seem to occur on flyweight Titanium/Scandium magnum revolvers shooting magnum loads. The recoil impulse on these guns is so savage that bullets are pulled from their crimps sometimes. It is therefore unsurprising to me that the gun could rotate under recoil briskly enough to leave the lock parts hanging in place under their own inertia, locking the weapon. This is a serious design flaw with the S&W lock and one that they should rectify, especially before some gnawed hiker corpse is found in bear country with his two-ounce riboflavin-framed .44 Magnum in his hand, locked up like Fort Knox.
If you absolutely must have a helium revolver chambered for he-man magnum loads, instructions are available on the big Smith & Wesson fan forum for disabling the lock by grinding off one little metal stud with your handy-dandy Dremel Tool, invaluable sidekick of shadetree gunsmiths everywhere.
From anecdotal evidence I have gathered, another component of these lock failures is that the locks on the subject weapons have all been used (or, in industry parlance, "fiddled with"). One reason I think that this is a component, if not a necessary prerequisite, is that the lock parts are manufactured via the MIM (metal injection molding) process, which is not known for turning out glass-smooth surfaces from the factory. Out of the box, this results in locks that have enough stiction that they are difficult to apply on purpose, let alone by accident. Were someone to take their new flyweight bear gun out and fiddle the lock back and forth to watch the little flag pop up and down, they would notice its application become a mite easier as the rough mating surfaces were bedded together by the repeated application of the key. One may rest assured that neither of the two lock-equipped revolvers I own has ever had the lock turned.
"What?" you say, "You own Smiths with locks?" Yes, I do, although I cordially dislike the little bugger on mostly aesthetic grounds. The two Smiths I own with locks are models that I wanted that had no pre-lock equivalents, so it was deal with the lock or deal without the gun. One is a steel-cylindered AirWeight .32 Magnum that is my everyday backup CCW gun, and the other is an all-steel large-frame .44 Special. Neither generates enough recoil impulse to make me worry about the lock at all. Incidentally, I also used to own a Titanium-cylinder .45 ACP revolver with the lock. The gun generated enough recoil to cause lightly-crimped ball ammo to jump its crimp, but in the thousand or so rounds I put through it before I traded it, it never had an issue with the lock. Again, I just don't think it had the Wheaties, recoil-wise.
One other reason I just can't get my dander up about this issue the way others have is that when an end user looks at those pictures on ARFcom, they see "OMG! A S&W LOCK FAILURE!!!1!!". I look at them and see "Ho hum. Another broken gun." Having worked in places with 'We Fix Busted Guns' signs out front for so long, I have seen so many firearms that have broken in so many ways that a new one fails to engage (pardon the pun) my interest. Frankly, if I had an AirLite .44 Magnum, I'd be as, or more, worried about the riboflavin cylinder failing or the little sheet metal tab in the topstrap getting eroded away and the frame getting flame-cut to uselessness as I would about the lock getting inadvertently activated.
A final grace note: I have to wonder how many people on those threads have shaken their heads at the sight of the jammed-up .41 Magnum S&W and pompously stated "Look at that! I'd never carry such an unreliable gun for self defense. Damn Smith & Wesson!" and then walked out their front door after stuffing their holster full of a semiautomatic pistol on which they have never performed One. Single. Malfunction. Clearance. Drill.