When holding down the fire button, even while reloading, using the Assassin's Shurikens, the animation of the gun firing occurs a couple of seconds before the first Shuriken actually comes out of the gun. This may be because of lag...
Yeah, this happens in the 360 version too. The character animation and the actual fired shurikens get more and more out of sync. The actual fired ones are slower than they should be. RoF endorsement might affect it. Lag definitely affects it, because it doesn't happen when hosting on 360.