I purchased my daughter a Ruger M77 Mark II here while back. I took it to the range yesterday to fine tune the sights. When I bought the rifle it came with two boxes of 80gr. bullets. We shot one box of them just plinking. I bought two more boxes of 100gr. bullets and tried to sight it in with those. I could not get a good shot group with those 100gr. bullets. I started at 100 yards and with the 80gr. bullets I had a 3 shot group in a 1" circle. I tried the 100gr. and could not get a 3 shot group within a 3" circle. I moved to 200 yards and with the 80gr. bullets I had a 3 shot group in a 3" circle. With the 100gr. bullets I could not shoot 3 shot group in 9" circle. So obviously the rifle prefers 80gr. bullets. My question to you is an 80gr. bullet enough to kill whitetail and muledeer at 200yards?