257 Weatherby will take a deer with good shot placement to 6-700 without too much trouble (or wind for that matter too). I've shot my 300 WSM
with 190's at 1140 yards on steel and 614 on a mulely buck. The muley weighed in at 287lbs and it was a lung shot using 180 gr Sierra Game SPBT. Blew through him with good expansion, He kicked up and rolled straight on his back legs in the air, almost DRT, but he moved backward about 3 feet.
I did the mule deer shot with a little burris 3-9x40 with their version of a BDC, I didn't use the reticule, just knew my drop and held over where I needed to.
Spend lots of time in the house drying firing your rifle on a small practice target, work on breathing and trigger pull. I recommend to my new shooters to do it 60-100 times a day if they can. Then get out and shoot the distance, learn as much as you can from your range time, you can't practice for wind and judging without being out in it and shooting through it. Good Luck!