I am thinking of purchasing an AR-15 Varmint gun and I need to figure out what scope to get for it. This will be a range gun and I have no plans of taking it to the field. The targets that I will be engaging (mostly paper and some steel) will be placed between 100yds and no farther out than 400yds. I believe that a 10x42 scope will serve my purposes but I keep debating whether I should get a variable scope such as a 6-24x42. I am not too concerned with different brands right not. I am mainly looking to choose the magnification factor first. Your recommendations are welcomed!