Mark the middle of the stripper clip with a pencil or better yet a metal scriber. Put the clip in a vice just slightly above the jaws of the vice. Level it and score it several times with the edge of a small triangle or knife edge file. Once you have a decent score mark, simply snap it off in the direction of the score mark. It should break easily. Crimp the cut ends gently with a pair of plyers. You don't need to crimp them very much, you will break them if you do. If you have access to some of that epoxy rubber that you use to dip tool handles in to make grips, you can dip the crimped ends in that to make that end easily identifiable and less likely for the loaded rounds to drop out or be inserted into the gun wrong.