I dont know about you guys, but our instructor always told us "never carry a semi-auto for duty or combat that doesn't rattle, if it doesn't rattle it'll likely jam on you". I have carried several S&W semis as well as glocks over the years and they have all rattled. Even the Sig 229 I carried was a rattler. One thing I've noticed on the .40 mags rattling, I've observed that they are also marked .357 sig. Maybe this has something to do with it? The ones for my M&P (that absolutely loves me and the feeling is mutual) sounds like it is coming apart, none of my older models did (4006, 4056, 411).

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Warren