I have a Bar-Sto .400 Cor-Bon barrel fit (by Bar-Sto) to my Kimber Stainless Target. I used the reloading data from the Cor-Bon web site, and found it way too hot for my gun. When I loaded my rounds to their EXACT suggested starting loads for AA #7, I was getting much faster velocities than what they list with their max loads. The chrono measured over 1450 fps with 155gr XTP's! These loads were obviously too hot for my gun, and the primers (and chrono) proved to be good tattle-tales.
I measured OAL for loaded rounds before and after chambering them to ensure that the bullets were not being pushed into the case. There was no difference with new brass, but when I used once fired brass, the OAL shortened somewhat. Now, I only use new Starline brass to avoid this problem, but I still have to load a full grain under Cor-Bon's starting loads to keep velocities within sane parameters.
I notice the new .400 Cor-Bon brass has a sm. primer pocket, but I haven't tried any yet to see if it makes a difference.
I would like to try a crimping dies similar to Lee's factory crimp die for bottlenecked cartridges.