Hotburn; Neat little gadget, eh? Your 50 yd will be right on too, in case you can pop a yote or rabbit. Where the duplex thins down is good for 10 yds. Did you have any breeze while shooting at 40? I've found it don't take much air moving to have me chasing my tail at 40 and 50, lol. I shot two squirrels today w/ Phoenix, one at 30 in the head and one at 36 not in the head, lol. Got the back legs and back off of that one. Have fun!