Dry firing does wonderful things to improve trigger control and sight picture. It is a mandatory drill with the 1911 !
traevin will give you the same answer as me (I hope - feel free to add your own .02 cents traevin!!!), I just happened to get here first.
It is not the racking of the slide so much, but the release of it on an empty chamber. One should never let the slide slam home on an empty chamber, as this causes the sear to bounce around and hit the hammer hooks, due to the shockof the slide hitting home. This shock will destroy the carefully matched angles of hammer and sear. You can ruin a good trigger job if you continue to do this. When you release the slide, always slow it with your hand, when practicing unloaded drills.
NOTE- This does NOT apply when chambering a round. Always let the slide move forward under its own spring tension.
[This message has been edited by shane45-1911 (edited 04-16-2001).]
Shane summed it up nicely. He's absolutely correct. It's a big no-no, but for some reason, people that should know better still do it all the time. For whatever reason, if you need to make sure the gun isn't loaded, just do a press check.
Jerry Kuhnhausen, who pretty much wrote the 1911A1 gunsmith bible, makes it perfectly clear: "Never dry fire a gun on an empty chamber no matter who says its OK." If there's one guy that knows how to baby these pistols, it is he.
Now - with that being said - I wouldn't own a centerfire that I couldn't dry fire without fear of breakage. I've come to realize what an important component the act of dry firing really is (especially in trying to improve my weak hand shot). Also, and I don't want to give the impression that I'm proud of it, but I don't use a snap cap or empty casing; and I dry fire a lot.
However, if I ever break a firing pin or any other related part, please trust me to eat a bunch of crow because I WILL post it here.