Yeah, it's absolutely true that the basic DA revolver (as made by S&W, Colt, Ruger or Taurus, doesn't matter) has a very low rate of accidental discharge. When the NYPD switched from DA S&W wheelguns to Glocks, the accident rate went up very significantly. That department tried ordering a heavier trigger pull from Glock (the "New York trigger") but it didn't help much.
There's several reasons for that.
It's easier to check the revolver's loaded state. Most of them, you can look sideways at the rear of the cylinder and see the shell rims pretty clearly. In those few you can't ("recessed" chambers) you can point the gun PAST your head (never "at your head") and see the bullets themselves from the front of the cylinder. All of this can be done without touching a single control. Or, you can release the cylinder, swing it out and look very clearly at the backs of all the chambers, which can be done without touching the trigger or otherwise risking an AD.
On the semi, to check the gun's loaded state you have to rack the slide and look into the back of the barrel, which in turn is in a relatively dark chamber area. It's not that hard to miss spotting a live round. Best practice is to lock the slide back (if the gun supports doing so) and poke your pinkie finger in there to make sure. But now you have another problem: if you've screwed up the order in which you rack the slide and drop the mag,
the act of checking the chamber and confirming it's empty can load a live round into the chamber as you close the slide!!! In other words, you rack it back, look in there, it's all good, you drop the slide "knowing" there's nothing in the chamber and whoops, the slide going forward stripped a round off the top of the mag and crammed it in the barrel.
The order in which you do things is vital.
Two more causes of accidents on the semis:
* If you're an idiot and don't know what you're doing, you'll pull the magazine out and "yeah, of course it's unloaded, I just pulled the boolits out". You don't know there's still a round in the pipe. So you point it at your fellow drunk fratboy or whatever and pull the trigger. Ooops. Happens quite a bit, usually with kids involved.
* On some, notoriously the Glock and a few others, the take-down procedure for cleaning involves pulling the trigger. So if you've screwed up the whole "is it loaded?" thing, you WILL crank one off. This is probably one of the top causes of the NYPD's problems. On the wheelguns in contrast, you never have to touch the trigger during cleaning, ever, for any reason. Obviously you should NEVER clean a loaded gun but this mistake on a wheelgun usually doesn't result in a problem. At some point when you do open the cylinder you'll see live rounds in there and curse yourself for a dummy, but...there was no loud noise before that point unless you "tested the trigger" or something.
Weird post-script: the safest sort of handgun of any of the repeaters is probably the single action types that have a transfer bar safety grafted in, such as the 1973-and-later Rugers, the Beretta Stampede series or a few others. They're as drop-safe as any of the best handguns made, semi-auto or DA wheelgun. Pressure on the trigger can't make them go boom unless the hammer was cocked first. After every shot, the hammer falls, putting the gun "on safe" - you can't accidentally squeeze off a second round via flinching. People who still ride horses and carry a gun often prefer SA wheelguns for this reason, not because they're "playing cowboy".
If you're on the back of a horse and have to shoot at a threat, be it human or animal, the dang horse is very likely to buck and jump either from your gunshot or the threat, or your attacker shot the poor thing. In that case you'll try and hang on with your off-hand, and the sympathetic grip effect will cause your gun hand to clench up too. With an SA wheelgun, this isn't a problem, you won't send a second wild shot off to God knows where.
Extra training is required to get the "cock and fire" drill down pat of course.
Issues like this are why the Ruger Single Six and Bearcat work so well as a kid's first trainer handgun...they're unlikely to accidentally crank off a second round and the adult standing behind 'em can tell if the thing is cocked or not.
ON EDIT: one more detail. S&W DA revolvers made before WW2 have a sub-standard hammer-block safety. They're not 100% drop-safe. Best practice is to avoid carrying one for personal defense, unless you have nothing else available. I would also be wary of older Taurus revolvers with importer's marks, dating from before Taurus set up their own import company in Florida. Basically if it's an old Taurus with another company's name on it too, it's...really ghastly quality
.
Welll...OK, one more thing
. Some of these DA guns will have a hammer-block safety, that blocks the hammer from falling unless the trigger pulls that barrier away. Done right, this is a perfectly reasonable system, with an interesting advantage: the mainspring can be up to 25% less power than with a transfer bar ignition and it'll still work, which is one reason classic S&Ws had such sweet triggers. Transfer bar guns are sort of "opposite": the hammer is set up so that it cannot hit the firing pin, period. When the trigger is pulled, the transfer bar rises into position between the hammer and firing pin, "transferring" the energy to make a boom. If a hammer block breaks, the gun reverts to "no safety" and will likely fire if dropping with the hammer on a live round. If a transfer bar safety breaks, the gun turns into a doorstop - can't go boom no matter what you do. Both will successfully keep a gun from going off if dropped, with the notable exception of the older S&W system which "can" fail. Sometimes.
