RidinLou,
In US Field Target there are several different classes. International or WFTF class is limited to 12 ft. Lbs, and there are separate divisions for spring guns and PCP's. All other classes within AAFTA (AMERICAN AIRGUN FIELD TARGET ASSOCIATION) have a limit of 20 ft. Lbs. These classes include Hunter PCP, Hunter Springer, Open PCP, Open Springer.
There are a good deal of countries that have a 12 ft lb. limit due to their laws, which is why there is a 12 ft lb limit for international class.
USA also has Pistol classes, and that has a 12 ft lb limit as well.
Some guns are specifically designed for 20 ft. Lbs, and some guns are specifically designed for 12 ft. Lbs. It is common to get either of these platforms and tune them up, or tune them down, depending upon what class the shooter competes in, and personal taste in guns
Tom Holland
Field Target Tech