I have a Viper 4-12 AO with the BDC on my wifes .270 wsm and we love it. She shoots it well. Here is a cow elk that she took with it this last year at 360 yards.
With this rifle scope/set-up, it killed a yote at 405 yards last year also. We have been shooting it a bunch this year and she has killed multiple basketball sized rocks out to 560 yards this summer.
Great scope for the money... plus I believe Vortex is running a $50 Manufacturers Rebate right now.