Can't quite tell from your post, but if you shot all of those different bullets, or even some of them, during the same trip to the range, there could be a couple of reasons why the first ones seemed to be the best. Your rifle barrel could have gotten heated up which would account for widening groups, or your barrel could have gotten fouled by the earlier rounds. It doesn't take many rounds to effect groups. Also, if you were shooting a new rifle, did you break it in properly before you even tried to decide which bullets worked best?