I've used a 6x20 Leupold that was boosted to 18x40, with a target dot installed by Premier. Very good scope for small bore sillouhette. It was placed on an Anschutz 54 in conjunction with a level at the end of the barrel. If the bubble was level, and the dot on the steel, the target was toast.
The downside- the high magnification really showed how much you move and how heavy you breathe. Mirage could be a bear as well.
The upside- those tiny chickens looked huge in the scope, and the turkeys and rams were pretty good size too. The boosting gave more target to hold on.