My daughter took the SW99 to a basic pistol class and brought it back with the plastic sights broken. What a surprise. I got the Walther P99 metal sights and had them placed on the SW99 by a gunsmith. Front went on OK but he could not get the rear sights on. I examined the Walther metal sight base and found it to be less than one mm wider than the SW99. Thus he could not get it to work. I say bull shit as he could have shaved off some metal. Anybody have knowledge on this problem or ever placed Walther metal sights to a SW99?

Ask over on the smith-wesson forum. There's a former S&W armorer who can definitively answer this.