It finally happened. I'm 74, have been shooting since I joined the Marine Corps at 18, and just the other day I had my first and only negligent discharge.
I own and regularly train with three different Kahrs: a PM9, an MK9 and a K9. They all have similar triggers, with a very smooth, long, revolver-like pull. Recently, I added a Sig P220 Equinox Carry to the mix. That pistol is hammer fired, DA/SA, meaning the first pull of the trigger is quite long and maybe 9 pounds, while subsequent pulls are extremely short and maybe 2.5 pounds. Light, in other words.
The other day I went to the local indoor range and took along the K9 and the Sig. I fired about 100 rounds through the Kahr, then switched over to the Sig. I fired a round out of the Sig, then paused to look at something and let my gun hand fall to the table. Just as I began to raise the Sig to the firing position, it suddenly discharged. It was pointed approximately downrange and the bullet went into the floor. No damage or injuries, by the grace of God.
What happened? After a great deal of thought, here is what I believe occurred. I had been used to the Kahr trigger, which has a long pull. I believe that I had gotten into the habit of beginning to stroke the Kahr trigger before the pistol was at eye level and the target was in the sights. As the pull was long, the action, though wrong, had no consequences. However, when I subconsciously did the same thing to the Sig trigger while it was in SA mode, it was enough to cause it to fire.
Shocked and shamed at the same time, but some lessons re-learned:
-- An ND can happen to anyone, no matter how experienced. Even me. Even you.
-- Finger off the trigger until target is in the sights and ready to fire.
-- Be VERY careful when operating two weapons with completely different manuals of arms.