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?

IMO, 80 grains is a very low mass for deer hunting, but I think it will still be effective at shorter (inside 100 yd) ranges. My own personal setup may be a bit on the heavy side, though - a .270 firing 150 grain ammo.

Nate