8x56..Thanks for the info, I had a similar incident a long time ago with an old Sears shotgun that had a polychoke on it, for some reason, and it could have been because it was crooked, it would put the pattern either way right or left, dont remember which. But I do remember that I did some filing on the collet and got it much better. However I had never heard of adjusting impact with slugs in a similar manner. The more I think about it, the more I am intrigued by it. If I could find a suitable shotgun to experiment with I think I will try this.