Sounds like fun, If you want to make this a contest you need to make it realistic because a "Black Rifle" is not something realistically equipped with a 3 foot long 25x super sniper scope so optics should be limited to something you would actually use realistically on your black rifle or I call shenanigans

I have a 5x AR-536 scope on my Tavor so 100 yards is a pretty small target even at 5x so the person with the biggest super scope to zoom in will shoot something unrealistic. One reason black rifles are not super accurate is because of the optics normally put on them lets you hit something a couple hundred yards out but not being high powered scopes it limits their accuracy overall.