From the University of Kentucky
http://sweb.uky.edu/StudentOrgs/Trapand ... lTrap.html
International Trapshooting differs from American Trapshooting in one very important point: IT IS MUCH MORE DIFFICULT! There are several reasons for this increase in difficulty:
Number of traps
The number of traps in this sport are 15, not the single trap sitting in front of you throwing targets. For each position on the field, there are three traps in the traphouse (called a "bunker"). These three traps are set to throw one right angle, one left angle, and a straight-away. The traps here are fixed, in that they do not move back and forth.
Speed of the targets
The speed of International Trap targets are roughly twice as fast as American Trap targets. This means they are going about 90 mph.
Distance the target is thrown
In American Trap, the distance that the target is thrown is set at a certain distance. In International Trap, the distance is twice as far, but it varies. The three distances at which the traps are set at are 70 meters, 72 meters, or 75 meters from the bunker
Severity of angles and differences in height
In American Trap, the target can be thrown anywhere in a 45 degree angle from the middle of the traphouse. Also, the height of the target is fixed. In International Trap, the target can be thrown anywhere in a 90 degree angle from the middle of the traphouse, and the height of the target varies from 1 meter to 3 meters above the traphouse
In International Trapshooting, the load of shot that a competitor can have in the shell is dropped from 1 1/8 oz. to approx. 7/8 oz. This means there is a decreased number of pellets being shot at the target. With a decreased number of pellets, it is much harder to hit the target. The rules allow a 3 1/4 dram equivalent load (which makes the pellets go faster) and two shots at every target to compensate for the decreased number of pellets.
The target used in International Trapshooting is a little harder than a target used for American Trap. This makes sense since the targets are being thrown twice as far. The targets must be made harder to withstand the physical force applied to it while it is being thrown from the trap.
Here is a diagram of an International Trap Field.You have the "bunker" from which the targets are thrown.. A shooter will shoot one target and then move to the station to the right, and when the shooter reaches the far right, will start again on the far left position. The distance between the shooters and the bunker is 10 meters (approx. 16 yards). There are marks on the bunker in front of each shooter representing the middle trap of the three trap for that station. The trap under that mark will throw a straight-away, the trap to the right will throw a left angle, and the trap to the left will throw a right angle. A round consists of 25 targets, and a typical day of shooting for a match will be 100 targets.