+1 on Win 69's comment.
I use a Forrester outside neck reamer and do the math like Win69 said and turn the brass down in two passes. Once to get close and the second to get it exact. Don't go fast just take your time. I also use a Redding neck sizing die with the right insert to get enough neck tension. Every now and then when the cases get too large to fit the chamber easily I will use a full length size die to bump the shoulder back.
Its a real PITA to do cases this way but I'm only doing this on a gun I hunt with that I want long range accuracy with and when I did the cases I only did 200. I put 100 away and just use the first 100 to reload and when those are gone I will dig out the second 100. So far I am a long way away from digging out the second 100 as with a load that isn't too hot you get little case growth and the cases seem to last forever. I figure when the cases are gone the barrel with have long been worn out. Next barrel will not have a tight neck.
At this time I have two rifles with tight necks but man I love the way they shoot.