6.5 brass is sold for small and large rifle primers.
Many prefer the small rifle primers because they say the brass is tougher, it will last longer with loads near or slightly above the upper limit. Something like that.
One day I messed up, I didn't look at my notes and I reloaded a bunch of LRP 6.5 brass over the max loads. I forget but something like 1 grain over the max. I had a bunch of primer pockets expand. Some to the point a primer would fit too loose. Some, the primer was slightly loose but could still be loaded (keep in mind the brass had already been reloaded a few times). I went back down to normal and didn't get any more loose primer pockets, even the ones that were already loose didn't get worse.