Mirage comes from 2 places. One from down range, not much you can do but learn to read it (Like 45-70 states) and really pay attention to it.The other Place is from barrel heat. When I shot Benchrest we used several things to combat this last one. We would use Strips of targets, Venetian Blinds, corrugated plastic, old Xrays, etc. Cut a strip long enough for the length of the barrel from just under the scopes objective lens to muzzle. Then attaching to 2 pieces of Velcro. needs to be wide enough to direct the heat waves out past the lens in the scope, so 2 to 3". Sun shades only do so much but can't get rid of it all. There used to be a company that made a frosted tube that was real long. I personally would not use one of those as the Wind blowing against it can affect the scope, if your unsure about this put the rifle in your bags and while holding the rifle still press on the side of the objective lens. We only used the standard 2 or 3" sun shades that came with our scopes because of this. Some ranges have boards painted with horizontal, alternating Black and white stripes to assist in reading the mirage, it can help with reading the mirage.