At the Redwood Gun Club range next to the Pacific Ocean, we use either the ASSRA or Wyoming Schuetzen Union (WSU) targets, depending on the whim of the match organizer and what we happen to have in quantity. The dimensions of the rings are the same, but the colors vary slightly. The ASSRA target (sold only to members) has an orange-red center on one side and black on the reverse. Some shooters find the red center easier. Some others find the black center easier. It is a matter for individual eyesight which works best for you. But sometimes the Schuetzenmeister is cranky and says "only red" or "only black". The WSU target (sold to anyone with $) is reddish color, of a darker shade than the ASSRA target. On one side, the rings from 24 to 18 (as shown in above photo) are red. On the reverse side, only the only the 24, 23, & 22 rings are colored red. That side is for shooting with scope sights.
We are not great observers of formality. Scoring for hits on paper depends on the whim of the Schuetzenmeister. Sometimes it is 5 points for hits on paper. At other times, hits outside of the 10-ring count zero. All scoring is on the honor system. Most of us are there simply to have a good time.
There is also a WSU target for 100 yards. The 25-ring is 3/4 inch (19 mm). Each ring increases the diameter by 3/4 inch. The red circle is 6" in diameter and the 10-ring is 12" in diameter.
We allow either traditional German rifles with traditional sights or early (pre-1917 design) American (or other) single shots with traditional American sights.
Some of our rifles have only scope sights, but the scopes used must have external aiming adjustments on the mount, not included in the scope. I think one must be a very good shot to take advantage of the telescope. Otherwise the scope merely magnifies the wobbles.
We say "pre-1917" scopes, but I think some of our most skilled traditional telescope makers were in the German Army in 1917.
waterman