When I sat down and watched the video a few more times I was really taking notice as to where the rounds were hitting. I knew that the first 4 rounds were XM855 and the last 4 were XM193. With that information I went shot by shot and mapped out where the rounds had hit on the plate. Had we not used the plate carrier, it would have been instantly obvious which rounds went through. The XM855 hit in the lower section of the plate, but I had thought they hit higher, instead the XM193 rounds hit where I thought the XM855 had.
So I was wrong in my reporting of which rounds actually penetrated the plate, for that I apologize. However the plate was still defeated at 25 yards using XM193. The reasoning behind this round defeating that plate is that the XM193 is moving well over 3000FPS. When it comes to steel, it is the velocity of the bullet that will defeat steel, not the weight of the bullet. I believe had the steel been thicker the chances of stopping this round would go up, but at 1/4" thick it just is not enough to stop such a quick bullet.
XM855 Impact Point