I have hunted both elk and mule deer with a T/C Contender in .357 Herrett and 7-30 Waters and have had a lot of fun doing it. The longest shot that I have taken was on a 3x4 mule deer with the 7-30 Waters with a 120 grain bullet at 2900 fps and he droped in his tracks. One of the elk that I took with the .357 Herrett droped in her tracks at a little over 100 yards. I have also taken two bull elk with the Herrett with no problems and one with the Waters witch took a follow up shot but it really wasn't necessary.
So if your friend is hunting with a .308 in one I would tell him not to wait until the last day but to start out from the begining with it and enjoy it.
If you're lucky enough to be on private land and can leave your stand up during the off season you can tie an old piece of cloth or something of the sort to your stand. I like to use an old camo bandana that I have. That way the deer get used to the movement and eventually don't bother even looking up when there is slight movement. This may just give you the time to draw your bow or raise your gun without being detected.