Honestly man their are very few offerings in factory rounds that aren't good out of a 270 out to 300 yards for deer sized game. Just realize you prob shouldnt sight it in at 100 etc..and feel like it'll be good for all of the rounds your buddy gave you. If you put them into groups of identical rounds you should sight it in for each group.

Its not just up and down POI you have to worry about but also left and right. I can reload say 3 different loads with identical bullets just different amounts of powder or bullet depth and the left to right and up and down can be off 3-5 inches sometimes.

If you purchase new shells, the cheapo Winchester, Rem CL's or Fed's 130-150 will all work perfectly fine for what you are trying to accomplish. Buying the expensive ammo doesnt automatically mean better groups and premium bullets aren't really needed on deer sized game.

Good luck and make sure you take the time to pull stock off, pull bolt out and clean it. Any new or new to you gun should get some TLC before you shoot it. Double check all screws are tight when you put it back together. I just never trust someone else's rifle until I take it apart clean it well and put it back together.