I'm also the match director for the Benchrest Silhouette matches at Farmington NM. The game was brought from El Paso about 15 - 17 years ago. Here is a drawing of the size of the targets we shoot. On the fox and coyote, the dimensions are to the sweet or largest spot on the target. On the gopher, owl and rabbit, the dimensions are the width at the widest part.
They are shot at 65, 75, 100, 150 and 200 meters. We do have a sight in period before the match starts and we also use surveyor's tape at the berms. We must shoot 10 shots in 5 minutes. Rifles used are anything from 10/22s Savage, CZ, Anschutz, 40X, 52s and full customs. We have a weight limit of 15 pounds, no one piece rests and any power scope. Ammo used ranges from Wolf MT to Eley 10X. Typical winning scores on a bad day is 44-46 and 47-49 on a good day in the master class. A good day for us, because we shoot on the top of a mesa, is a hold off of less than 5 inches at 200 meters. We have four classes A, AA, AAA and master.
These targets look huge compared to what you guys are using but in the 15 years that we have been running the match, we have had only two perfect scores of 50 targets and I have been lucky to have shot both. BTW, on a bad day, we can be holding off 15 to 20 inches.
This is not a game that requires a super accurate rifle but does require good wind reading ability and confidence that you know how to adjust your scope for each range depending on the changing conditions and you know how much to hold off for that first shot.