Which scope is best for Browning 7mm rem mag?

It all depends on how serious you are. I'd stay away from Bushnell. Yes they do make some higher end optics but they also make some real K-Mart $29.99 junk. I hear Nikon is pretty good but I have no experience with their scopes. You mentioned a budget of $400.00 so that tells me you are not skimping, check out Leupold. My opinion is that they make the best scope for the money. It is made in the U.S.A., nitrogen filled and have a life time warranty. That's what I use and have never needed the warranty.