Some gun jargon is causing confusion for some folks. For quite some time I have been getting a number of hits to this site with searches for “Where is the pre-lock on a gun?” or “What is a pre-lock on a gun?” Let’s see if we can help.
When folks refer to a “pre-lock Smith & Wesson” they are referring to revolvers made BEFORE S&W started installing their built-in key LOCK system on revolvers. I don’t care for revolvers with the locks and will not own one; it is a personal choice, I just think they are bugly. Some folks just do not trust the locks, they worry that recoil may engage the lock during a critical incident; I do not have the expertise to comment on this concern.
In the above photo (taken from here) the lock is the hole in the side of the revolver just above the cylinder latch and below the hammer. You put a key in the hole and give it a twist to lock the action so the trigger will not pull (NOTE: I don’t believe the lock is intended to be used on a cocked revolver; this photo is alleged to be of a lock failure). A pre-lock S&W does not have this lock.
Now, there is always a chance that I am wrong, some guns may indeed have something called a “pre-lock,” and I just have never heard about it. After all, guns have been around a long time and there have been matchlocks, wheellocks, flintlocks, caplocks, boxlocks …
In fairness to S&W, there are other brands of revolvers and pistols manufactured with built-in key lock systems. Further, S&W recently has been offering some revolver models without the locks.