I own two Model 70 Short mags., a 300 WSM
, and a 270 WSM.I have not had a problem with bolt thrust on either gun, even though I am aware that because the short mag brass has a smaller surface area that comes in contact with the chamber there is a potential problem. This sometimes has shown up when you fail to clean and dry the chamber after you have cleaned the barrel. I have shot many rounds in both guns without this ever being a problem.
Both of my Model 70's were built just over ten years ago, so I can not speak for the current Model 70's but both of my gun have a mag that is long enough so the bullet can reach the lands and still fit the mag.
Are you looking to buy a current gun or a used one made some years ago?
I have used Norma brass most of the time, however I have used Remington, Win, and Federal. The brass is not a problem for either gun.