personally, I recommend using SAMME specifications/chamber reamers and adjust the bullet for best Performance.
Building a rifle around a bullet can be risky, It the barrel doesn't like the bullet your done.
SAMME spec. chambers are designed to work well with most all bullets as long as they are loaded properly and within SAMME spec.
I used a SAMME spec. 7 RM for 1000 yard matches and shot 168 SMKs with great success, and loaded to extreme accuracy with ease. so don't over think the chamber dimensions and you will be ok.
Just My Opinion
J E CUSTOM