Interesting rules, I see it says carbines. I shoot a 21 inch barreled FAL in 3 gun. Not exactly your typical carbine.
Some of the big time matches have weight restrictions on rifles as well. Like the SWAT magazine world championship match, but I think the limit there is 11 pounds for those of us shooting FALs, M1as, and AR10s.
The weight limit is one rule I would probably ditch if I was in charge. Sure you could have a 14 pound .223 rifle, and sure it would have no recoil, but then again, most stages have lots of close targets that will most likely be engaged free hand. I don't think they would get very far ahead that way.