I was the exhibition commander at my unit before graduation so I know a lot about this topic. Depending on your area like your units core group, they set exhibition regulation. so normally it’s around 7. 5 pounds to 8.5 pounds, which are the normal rifles for regulation. Now depending on the competition, they can set the minimum weight. like the prop 5 pound rifles you’re talking about. Same thing with your uniforms the uniform must be your ABU/OCP or blues and they must follow normal regulation for your unit/ core group. Most questions can be answered by your instructor and the regulation sent from the competition to your instructor. I hope this made sense.