my 6,5x54MS die set( a 6,5x53R rimless) came today and so I start making 6,5x53R out of 303 Brit military brass. I was feeling - after years of reloading you have it in the finger tips - and seeing the shoulder of the 303 brass was a little bit brittle so first step was full length with a 308 Winchester die. this sets the shoulder back and was than followed by a 6,5x57 full length die for giving the neck a good start.

from left to right
303
303 shoulder collapsed
fl resized in 308 Win.
fl resized in 6,5x57
fl resized in 6,5x54MS
cut to 53,5mm
original 6,5x53R

this way I lost only one other case from 150 when the neck was sticking in the die

hope this could help, you can take a 6,5x55 FL die also