apparently colt used alot of variations on there bolt carriers over the years but the carrier is probably how it came from the factory.
http://ar15.com/archive/topic.html?b=3&f=118&t=554891
if it cycled fine with the other bolt carrier group obviously something is wrong with yours might check the gas rings again and check the gas key could be loose or have a broken bolt.
more weight should slow down the action and actually be more likely to short stroke than the lighter carrier.