My Kicks .660 and .665 both shot very well with the Old Rem Hevishot 3" 1 5/8oz #6 load, the old white Hevi shot 3" 1.75oz, Hevi 13 3" 6's and I am going to start on the 3" 7's.
Good luck with the response you want from Kicks. I called a couple of times about it. I usuallly got a different answer everytime. Kicks are made from the 17-4 stainless just like all the other tubes and they are very thick. Comp-N-Choke has had problems with heavy shot but they are not near as robust and the porting is 100% different.