Casting Corner by Rene Hesse 
Have you tried to make casts with a Wooly Bugger, Dumbbell Eyed or weighted fly and have the end of the leader ‘kick over’ and swing around at the end of the cast? Have you noticed being accurate with a weighted fly is often difficult? What causes that fly that is traveling towards the target to suddenly go off to the side for no apparent reason? Have you come up with the reasons in your mind yet? Here is thing that usually caused this to happen: the leader. Check it out next time you tie on a weighted fly.
The leader construction can be quite the science, but here is a simple way to combat the kick. When you have a heavy leader to turn over the loop with the heavy fly, it will often carry all of the energy to the fly without much energy dissipation. That energy shocks the end of the leader and kicks off to the side. If you see the kick and can’t correct it by applying less power to the cast, try this.
Adjust the length and or the diameter of the tippet. Here are two ways to make the adjustments.
If you need to stay with the heavier leader, i.e. a 0X, for a bigger fish, try adding another 18 inches of the 0X. Transferring the energy over a longer distance may be the answer. If that didn’t work, the other option is to take the 0X and add a length of 1X or 2X to reduce the mass profile of the line and reduce the energy transfer through dissipation.
To put is simply, if you are getting a kick at the end of your cast, try reducing the power application of the cast. If that doesn’t do it, add a foot or two of leader. You will be surprised how easy it is to fix the kick. The joy of casting will return, and so will your accuracy.