If you want a 40 degree shoulder on a 6.5x55 TC where you can't set the barrel back you just have to build 6.5x55 Improved, not an Ackley Improved. To form brass you have to open the neck to a larger size and the take it back to 6.5 and form a false shoulder for the case to headspace on. After that you can just use a set of 6.5x55 AI dies just being sure you you set up the dies so they don't push the shoulder back too far, There are a lot of improved cartridges that don't use a crush fit to be able to shoot factory rounds. Off the top of my hat the Gibbs line of wildcats come to mind.
