There has been a lot of reaction to the presence of various internal locking systems introduced on various firearms. I, for one, certainly wouldn't be surprised to see this as a trend of things to come when it comes to new production firearms ... but that's another subject ...
Anyway, I've listened to the reactions of the vocal folks who oppose the presence of the internal/integral locks, whether fool-proof or not, as well as the folks who find them useful and practical for their needs ... and everyone else who vacillates back and forth or falls in between.
I've talked to several folks at S&W who have a lot of experience with the revolvers produced with the locks. They've been pretty puzzled by the complaints of unintentional lock engagement. I've been repeatedly told the locks were exhaustively tested in their revolvers before being incorporated in revolver production, from the lightweight J-frames all the way up to the .500 & .460 S&W Magnums. I've also been told that they've been unable to duplicate the unintentional lock engagement, as long as the locks were installed properly and hadn't been tampered with ...
I'm as skeptical as the next person when it comes to change, though, and since I'm not a 'specific brand loyal' kind of guy I've been listening and watching ...
I've handled and fired a number of S&W revolvers equipped with the locking system, including J-frame Airlites and a couple of X-frame .500 S&W Magnums. No problems with unintentional engagement.
I've observed a number of other folks shooting new S&W revolvers equipped with the locks. No problems observed and no complaints heard.
I finally bought a new J-frame MP340 equipped with the lock. Shot it with standard pressure and +P .38 Spl, as well as shooting upwards of a hundred rounds of various .357 Magnum through it. Ouch. Dry-fired it until my finger couldn't cycle the trigger. Rested and did it some more. Did it on different days. Lost track of the dry-firing. No problems with unintentional engagement of the lock.
Being a curious LE armorer-type, I examined the lock arm and the torque locking spring. Interesting. The installation of the torque lock spring is a bit tricky when it comes to securing the short leg within the locking arm, and the longer leg must be properly positioned within a small recessed slot in the frame. I can see how it might be improperly installed if someone was distracted or wasn't paying attention. The small size of the lock arm's torque lock spring makes for difficult handling, if nothing else.
I noticed the current lock arm for the E/J frame guns (Part #29373) is Revision E, and the torque lock spring is Revision NEW. Of course, this may not mean what you might think, on the surface, since S&W is constantly making refinements & revisions to parts, getting them from new vendors or getting new versions from vendors, etc., etc.
For example, on a recent parts order 6 of the 8 various types of parts I ordered had various Revisions listed in the name/description. On another invoice where I ordered 10 various parts, 9 of them had Revisions listed in the descriptions. Pretty normal for them.
I think that almost all of the magazine springs I've been ordering in recent years have all been marked with a Revision number or letter, or both. How about a magazine spring listed as MAG SPRG REV A1 CH-244 REV.M2 ... or MAG SPRG REV. L5 ... or MAG SPRG CH244 REV. L1 ... or MAG SPRG REV. NEW?
Anyway, and oddly enough, a couple of problems I've recently encountered with S&W revolvers have involved a sear which wasn't properly fitted (causing the sear to stubb on the rear of the trigger, locking up the revolver when firing Magnum ammunition), and it was in an older 'pre-lock' revolver ... and a DCU (Doesn't Carry UP) timing issue where the cylinder didn't consistently lock on all charge holes before the hammer fell. Nothing to do with internal locks, believe it or not.
I've had other issues with S&W revolvers which were produced 'pre-lock', too, some going back to the 'good old days' when they were being produced with pinned barrels. A couple of examples are a 649 .38 Spl Bodyguard that came out of the box with a trigger that wouldn't return and a 629 Classic which exhibited Push-Off, and which had a hammer & trigger so far out-of-spec that it required a replacement hammer & trigger in order for the condition to be corrected.
On the other hand, I've had a couple of NIB S&W revolvers which were seemingly terrific right as they came from the box ... one had MIM parts and the other didn't. Go figure.
It's not just S&W revolvers, though. I could talk about problems I've had with other makes of revolvers, as well. Don't get me started on some Rugers.
Things happen, and they'll likely continue to happen, especially when it comes to machinery produced by people.
I do think, however, that S&W ... and a few other manufacturers of firearms which I could name ... could stand some improvement when it comes to their Quality Control, though.
Just my thoughts ...