ORIGINAL: Davoh
Now for my soap box...
There is no good reason to use a 7mm Rem. Magnum(ESPECIALLY NEW SHOOTERS), for deer of any kind... sorry but there really isnt anything a 7mag will do that the .270 doesnt... accept make more noise and beat the snot out of you.
Best advise to prevent deer from running off... get a milder recoiling rifle and practice with it. Shoot at least 200 rounds from it, and only use the bench to sight it in. Get so as you can hit a golf ball at any range out to 300 yds on the range from field positions(no bench), and on the first shot. General rule of thumb, your effective range on game will shrink by about 20% from nerves alone. Your accuracy(potential POI radius from point of aim) will double under field conditions.
I'm going to call you out on that one. There are very few people in the world that can shoot a golf ball from 300 yards from field positions on the first shot on a regular basis. Baseball, maybe. Softball, sure. But a golf ball is a little hard to believe. A rifle on a lead sled with a grouping of 1" MOA will move out to 3" or 4" at 300 yards. That's what mostrifles is capable of without any human intervention, and those rifles would be considered pretty accurate by most. If the wind was gusting between 5 and 15 mpha gust or lack of gust of windcould create a clean miss on a golf ball pretty easy at 300 yards.