I took my Elk with a speers 150gr bt from a winchester model 70 30-06, it was about 425 yards. the big thing to rem is the bullet drop rate, if I am zeor at 100yds, I will be -1 at 200 , -6 at 300, - 18inches at 400yrds, and -43 inches at 500 yards. knowing this I knew that I had enough energy in my shot to take down the Elk with a well placed shot.

You don't need a 180gr round, just know your gun, with what round you have. what you need to do no matter what size round you shoot, buy a box of each load your interested in , and shoot them. find the box that groups the tightest, and use that. don't get hung up on a fancy named bullet. shoot the round that your gun likes the best. most factory loads are pretty good. Remember when shooting your rifle, if you have a floating barrel, do not put any downward preasure on the barrel when shooting(don't hold the stock and barrel together with yor forward hand). this can can cause your rifle to shoot different each time you fire it.

I have always shot a 150gr. because it will take down moose, bear, elk, and yet is not over kill for deer. I'd bet that my 30-06 is responsible for more moose and deer kills than hyw 43.
if you don't get time to practice with your gun I would say a min of 100 rounds a year, then maybe you need to load her up with the heaviest round you can get, just to ensure some damage is being done if you miss your mark.