Originally Posted by staindvans
does a newer style kaner back need to be any certain bore size in order to be bored out for freak inserts?
the general rule of thumb is to use a back that is larger than the biggest insert you will use. you cant use a .689 insert in a .680 barrel because the ball will have to squeeze through the step down and break
so if you only use a .670 insert, you can send in a .680 barrel and be fine