"How does the disconnector work?" I get that question a lot, so I thought that it might be a good topic for those seeking understanding of the gun.
Its technical name is "The Disconnect"...but it's actually more of a connector. I've often said that it's a connector AND a disconnector, since a true disconnector only arrests the hammer until the trigger is released, and allows it to fall back to the sear so that another trigger pull can fire the weapon. Among the simplest of true disconnectors is the one in the AR-15 rifle and its clones.
When the pistol is in battery and ready to fire, the disconnect is positioned between the trigger stirrup and the backside of the sear legs. When the trigger is pulled, the disconnect is pushed into the sear, causing it to rotate off the hammer hooks, and the hammer falls. If the disconnect is removed, the hammer will cock, but pulling the trigger won't drop the hammer, bcause there's nothing there to bridge the gap between trigger and sear.
When the slide moves rearward in recoil, the disconnect is pushed down into the frame by the center rail in the slide. When the disconnect is pushed downward, it drops below the sear legs, and the sear is now able to rotate back into position to catch the hammer hooks, and hold the hammer at full cock position. Since the disconnect is designed to allow a two axis movement...up/down and fore/aft...it continues to move rearward a little further, and is captured by the bottoms of the sear legs until the trigger is released...and then rotates forward enough to allow it to also be pushed upward so that the top of the disconnect sits in the half-moon shaped slot in the slide, and connects the trigger and sear, making the gun ready to fire again.
This two-axis movement is provided by the center leg of the sear spring, located in the grip frame. This spring is a three-pronged leaf spring that also resets the sear and grip safety. The spring imposes tension on the disconnect in two directions at once by means of a 48 degree angle on the backside of the disconnect body, just above the paddle. The leaf pushes the disconnect forward to free it from the sear legs, and works with the angle to also move it upward.
If the disconnect is worn, or out of spec...and can't move downward far enough to break the connection between the trigger and sear, the sear can't reset. (Unless you're quick enough to release the trigger before the slide starts to move forward after it recoils.) The hammer can't cock, and it will follow the slide. For this reason, the top of the disconnect should never be filed or stoned, other than to dress a sharp edge or burr at the corners. The tip shouldn't be touched, other than to polish it lightly on a non-aggressive material.
I like denim with a little J&B Bore Cleaner imbedded into the cloth, and denim alone will often produce a nice burnish if the part is buffed briskly on the material.
If the disconnector is too long, and can't move far enough upward into the slot, it can't make connection between trigger and sear. The hammer will cock, but the gun won't fire. This is where many people get into trouble with the disconnect. They figure out why the hammer won't fall, and shorten the top of the disconnect, only to discover that the hammer follows the slide...or in some cases, the gun goes into full-auto mode. I'll repeat the warning: The top of the disconnector should never be filed or stoned. If it doesn't move into firing pisition, the half-moon slot should be made deeper. There is a scraper available from Borwnells that is designed specifically for this purpose.
In case anyone gets the idea that they'd like to play with the disconnector length in order to purposely cause the pistol to fire in the full-auto mode... be warned...The gun can fire out of battery, and do serious damage to the slide, frame, magazine, your hand, your eyes...or all of the above. It's also illegal. Purposely modifying any firearm with the intent of creating a machinegun can land you in deep trouble unless you live in a Class 3 state, and you have done all the required paperwork. I strongly advise one and all to forget this little trick.