The toughest bullet listed so far is the Barnes TMZ. And since you are shooting a gun designed to shoot sabots and since NM allows sabots, I would recommend trying that first.
It also may be your best choice at longer distances. Flatter shooting than bigger bullets but heavy enough to take down an elk. And since you can use a scope, you will want something that is good out to 200 yards. Again, that bullet would do the job nicely.
BH 209 is the way to go IMO and your gun will shoot it. Anything in the 90-110 gr range of powder will be adequate
