First off I would keep your 270. It is a great caliber rifle and will do almost anything you want it to.
Secondly, I would have a nice sit down with the landowner and convey to him how confident,carefull, responsible, and ethicalyou are as a hunter, never taking skyline shots, never shoot in the direction of a building or if he has cows always ask where they are and be aware of their presence,and so forth. I am sure he will respond positively.
Good luck.