There is not a great selection of .45 cal bullets. I don't think Barnes makes anything bigger than 190 grain. Way to small for Elk.
The best bullet for accuracy in my opinion is the Deadcenter bullets. I shoot the 260 grain bullets. I have to order them from prbulletscom. I have killed Three Elk with them. That being said I am pretty selective with my shots. I have put them through Deer shoulders without a problem but hesitate to try putting one through an Elk shoulder. They will hammer an Elk with a broadside shot through the ribs. They expand well and leave a great wound channel. The three elk I have killed have been from 70 to 166 yards. I use 150 gr of Pyrodex pellets.
Platinum powerbelts would hold up well, but no where near as accurate.