I've owned a Sigma .40 for over a decade.
Mine is the original SW40F. It doesn't have the tactical whatchacallum rails that the current versions have. I've never had a burning desire to hang a flashlight on a weapon anyway.
Back when the Clinton high-capacity magazine ban was about to go into effect, I was looking around for a high-cap pistol because I figured it was "now or never." Two guys who worked at
Target Master in Garland knew I was looking for a high-cap piece. They knew I had a Performance Center Shorty Forty, so they knew I liked Smith & Wesson and knew I liked the .40 S&W caliber. They also knew I'd been kind of looking at Glocks. Not long after the Sigma came out, I went in one day and they're like, "have we got something for you." They had gotten two SW40F's, one for a rental gun for the range and one to sell. They said they had each emptied a 15-round magazine into one ragged hole about one inch around at 30 feet, off-hand. They said they'd never gotten a right-out-of-the-box Glock to shoot like that. So I tried the rental gun. I did about what they said. My hole was a little bigger, call it an inch and a half, inch and a quarter, something like that. It was more accureate than I could hold it. I liked it. So I went and read everything I could about the Sigmas and came back and bought the other one they had. (I paid $585. Remember, the high-cap ban was coming so prices on high-cap pistols and mags were inflated.) I shot about the same size groups with it that I did with the rental gun. Over the next few paychecks, I accumulated ten 15-round mags for it. (I still have four that have never been used, with the price tags still on them.)
I started hearing stories about Sigmas not being accurate. But the two I've shot were as accurate as I could ask for.
I did have one problem with it. Once in a long while, say once every 100 to 200 rounds, I pulled the trigger and got a click but no bang. You could see where the firing pin hit the primer hard enough to dent it, but not quite hard enough to fire. I mentioned this, in passing, to a gunsmith at Lone Star Guns in Plano. I was having him work on something else and just happened to mention the Sigma. He looked at it and told me the slide wasn't fitting right. He sent it off to Smith and they replaced the slide for free, even though I'm pretty sure the warranty had run out. Funny thing, this was during the high-cap ban and I didn't want them to "lose" my magazines. So I sent it in with no magazines. It came back with two 10-round mags that I did not ask for or pay for.
I figure they probably assumed they had lost my mags and so gave me two new ones.
First time I shot it after that, nearly every round, the slide wouldn't close completely and I had to push it closed. I started to get mad. That was a lot worse than the original problem. But it was a new slide and fit tight, and the gun was bone dry. I took it home and cleaned and lubed it and have NEVER had a problem since. I had probably put 800-1000 rounds through it before they replaced the slide, and I've put maybe 300-500 through it since. Not one malfunction of any kind. And I have shot it pretty dry once or twice since then. I think that first time was just because it was new and not broken in.
I don't know what to say about the comments people have made on the trigger. I've always considered it about the same as a Glock. But I've only shot a couple Glocks, none recently.
Yes, the grip is fat. But in my slightly smaller than average hands, it works wonderfully. A lot of double-stack pistols do not. Although it doesn't look like anything special, the one place Smith really hit a home run was the grip. It's one of the few things different from the Glock. They made a real effort to make it ergonomic for people whith all different sized hands.
I've said quite a few times that if I
had to go into a fight with nothing but a handgun, this is the one I'd want with me.
This weapon fits some of my requirements: u.s. make? 
, price, large cap. clip, light weight?, not a new design... Does anyone have experience pro or con? 
