I've had a Browning HP Clone stuck to one of these for over a year and so far no measurable residual magnetism. No matter though, even if there was I'd keep using it. I don't carry this gun regularly it's more of a "just in case" weapon. I love the FAST system, and I noticed at the 1500 over the weekend they now have a smaller version for compact pistols. I'd have to agree with the above comments, unless your leaving the gun exposed in an environment filled with ferrous metal dust, there shouldn't be a serious problem. Also, according to the internet, residual magnetism can be removed with a degausser like a bulk VHS tape eraser, or in some cases by simply striking it against a hard surface. Something about randomizing the molecular alignment.