I would seat deeper. You may not have much more room pressure-wise to add powder and would probably still have the same issue.
As long as you are not trying to fireform an ackley shoulder and are pushing the 270 shoulder back to the correct headspace dimension with the sizing die, I would seat the bullet into the neck so that the bearing surface of the bullet is just forward of the neck-shoulder junction(option 1).
At a minimum, I would seat the bullet with bearing surface halfway into the neck. (option 2)
It really depends on how the rifle shoots with the bullet seated deeper.
I prefer option 1, and usually have the freebore set for my bullet 0.020" off lands at this seating depth, if possible.