Handguns with silencers
Keith, you found the place to ask questions like that. I like to think I know about guns but in this thread I have to bow to some real experts. However in the spirit of things I will comment on your silencer question. As you probably know most any handgun can be equipped with a surpriser. Revolvers because of the air gap are not a good choice. Semi-automatic pistols often have to be cycled by hand and some have been altered to lock the action closed for max quiet. Small bore guns are by their nature easier to suppress and sub-sonic rounds will not have the obvious problem of sonic crack.
The US military seams to have decided that purpose built guns are the way to go for silenced weapons and I would like to hear from one of our experts on what has been tried and why. One gun that got some use on "black" ops. was a Ruger .22 built with a barrel that had an integral suppressor. My understanding is that Ruger admits to building them but won't say who bought them or how many were made. The US Army & CIA frequently deny any specific use by them, but too many grunts have seen them carried on ops. to make the denials creditable.
Lets hope that someone can flesh out my admittedly sketchy information.