Since Colorado I believe has restrictions on sabots, then you need a conical shooting rifle that is light weight. If you have some time, perhaps order a rifle from Doc White in a kit. You can get a White - Whitetail G series kit for around $230.00. This would shoot the 460 or 495 grain No Excuse Conical excellent. Give Doc White a call or email. He is a great guy to deal with I have been told.

Another alternative is a CVA Buckhorn .50 caliber. You could then load it with Powerbelts and hunt elk with that. Both of them can have a sling thrown on them and would not be all that heavy of a rifle...

A lot will depend on how much money you want to spend and how much time you have before you hunt. After all it takes time to work the rifle up into a good load.