One measure of the difficulty of a field target shot is the Troyer (named after Brad Troyer). At its simplest, a Troyer is the distance to the target in yards divided by the kill zone diameter in inches. (Obviously, this can be adjusted to meters/mm by multiplying by 2.32.) Thus, if a target is at 45yds and the kill zone is 2in, the difficulty is 45/2 or 22.5T. In practice, there are additional multipliers for various conditions such as targets over 45 yards, wind, "extremely" dark/light conditions, standing/kneeling positions, and uphill/downhill shots. A typical course would have a difficulty averaging about 25T with a spread of difficulties from as low as 10T to perhaps as high as 60T. A well-designed course can be used for all field target classes although the PCP shooters will typically outscore the piston shooters. When one is practicing for a match, a good approach is to shoot at targets (whether paper or actual field targets) with a difficulty of about 20T to start. As one gets better, the difficulty is increased (either by increasing the distance or reducing the size of the kill zone) -- a good rule-of-thumb would be to increase the difficulty by 5T when one can successfully hit the target 90% of the time. Eventually, one should practice at about 45T if they expect to be competitive at local matches and 60T for national matches.