There isn't particularly a "standard" gun, it will depend on a number of things, including where your department is based, how much money they have at that present time, and where you're likely to be on patrol. There are some areas that would be in much greater need of a better gun than others. In some countries, police officers don't have to carry guns at all! I have always found that police officers are happy to chat and give advice, though, so if there is one specific area that you would like to work in then I am sure that they would be happy to answer your questions.