Are you talking a 7mm Rem Mag, 7mm 08, 7x57 Mauser? Either way for a big game rifle many hunters like to sight in at 2 to 3 inches high of center at 100 yrds. That allows you (depending on your bullet drop) a point-blank-range out to about 300 or more yards in that 7mm.
I shoot a 7mag for all my big game hunting. A Rem 700 with a 3-9 Leupold and 150 gr. Nos Ballistic Tips.. I zero 2-3 inches high @ 100 yards, gereally 3 inches high. Hold dead on your deer, elk, lope or what ever and DON"T HOLD OVER UNLESS ITS PAST 400 plus YARDS. The biggest mistake I see hunters do is misjudge distance and shoot over the animals back. How ever tempting put the first shot dead nuts on the animal. Realize that the kill zone of a deer is large and gives you some plus or minus in elevation by a few inches. Best of Luck.
Remember it's just A way, NOT THE WAY.
As the allure of hunting big whitetails becomes more and more a passion for many, we are finding that the recent (historically speaking) popularity of hunting deer from a tree stand is becoming the way to do it. I'll make no statement either for or against that technique here. This will be simply an essay on what I feel are some outstanding rifles for tree stand use.
Before we go even one more step, let's all remember that safety is first and foremost for anyone wanting to hunt...