The #1 cause of problems like this is a magazine that is not seated. The first round will feed, but pushes the magazine down so that the 2nd does not. As most people drop the magazine and clear the chamber as they check the stoppage, they never realize the magazine didn't go "click". Base pads are an essential add-on for flush-fitting magazines, IMHO.
That said, whenever I see these polls about people feeding n,000 rounds through a pistol without a single malfunction, I take them with a large grain of salt. In any military firearms training, significant time is spent on immediate action procedures when the weapon does not go boom. I'd expect some sort of malfunction every couple of hundred rounds - with anything - and practice accordingly if you are a tactical kind of guy.
SIGs are excellent pistols but the feed ramp isn't really polished and if you are shooting average dirty ammo like Winchester White Box, you'll see a layer of residue built up after less than 100 rounds. That's why street reliability jobs usually include polishing the feed ramp along with the action work. Some people simply rub the ramp with a fine abrasive, while braver souls attack with Dremel. I leave it to the pros, personally.
