Your recollection of "such a fast, small round that it wasn't doing any knockdown at all....just passing on through" was a phenomenon reported by our troops in Somalia, as well as later in Afghanistan, where the adversaries were not "trained by Hollywood" to fall down when hit, and instead kept going until actually physically incapacitated (and aided by indigenous substances such as khat). The tunsten tip of these rounds, while effective on vehicles and covered targets, did have a tendency to simply drill a pencil-diameter hole through the bad guys.
In Afghanistan, the 77-grain ammunition has been put into service for the last year now, and has a much more severe wounding effect, as well as better terminal ballistics at longer ranges.
