Originally Posted by Ian
Ten years ago I came across a small monograph on the topic of bat on ball, but I seem to have mislaid it. Perhaps someone else has seen it. It had a nice discussion of the forces in play and how these contributed to distortion of the shape of the ball and how far it traveled. It talked about the percussion point as being an important consideration of how effective the bat would be when connecting with the ball.
For bats and rackets, the centre of percussion certainly contributes to the sweet spot. For swords where the rotation is about the grip (or at least, the wrist), like sabre styles where the sword is held in front of the body, and the hand stays fairly still, it's also important for where the sweet spot is.
However, for swords where the rotation is about the shoulder (i.e., the whole arm moves), it isn't particularly important for impact. It's still important for handling, because when you move the hilt sideways, the centre of percussion will want to stay still. Thus, if you have the COP at the tip, the tip will stay still, and you get very nice point control (hand-and-a-half longswords and jian are often balanced like this). Or for swords that are expected to be in contact with an opponent's blade or shield (like arming swords for sword and buckler, or rapier), you can have the COP at the expected point of contact for easy rotation of the sword about that point.
But since a shamshir isn't used for hand-stationary cuts but rather for slicing draw cuts from the shoulder, and isn't used like a jian or rapier, or arming sword with buckler, I don't think the location of the COP matters, and I'd expect either of two things: (a) the COP at about 8" from the tip, because that's common on a wide variety of sabres (especially Western, but also common on talwars and katanas and other Asian sabres), or (b) the COP to be just wherever, with no systematic placement (which, as far as I can tell, is how the COP is placed on most Chinese dao).
PS: the pendulum test (i.e., finding the position of the centre of oscillation (which is the same as the centre of percussion)) is probably the best way to find the location of the COP of a shamshir. I don't trust the waggle test of very curved blades.
[I should put together something systematic and detailed on the COP. If time permits ...]