I have a friend who shoots a 300 win mag. It is a Sako do not know the model he bought new in the early 70's. We both reload and he has been shooting the same loads since it was new. It suddenly developed a problem with chambering. He has tried full length resizing and trimming to 2.610 to no avail. I have a set of small base dies for a BAR in 300 win. Even after full length sizing through the small base dies it would not chamber. After trimming his brass to a length of 2.603 the rifle will now chamber with slight pressure. Anyone have any ideas as to why all of a sudden this would occur? I suggested he take it to a gunsmith as I am not one. I do not feel like the brass should be trimmed that short. Thank you for your help.