I am reading some talk about the USG, what is the difference? I am new to FN and hope to buy my first (FNP45) next weekend. From what I can see on the FNP website it seems to be the color, is there anything else?
SAO - Single Action Only. Means the same as on a revolver, the hammer must be manually cocked before firing. Only difference on an autoloader is that all shots subsequent to the first, the hammer will be cocked by the action of the slide.
If you've ever played with a 1911, that's probably the most famous example of an SAO autoloader.