Use the heaviest Barnes X bullet you can get.
If you reload try the Barnes 140gr triple shock. People have been getting excellent accuracy with the triple shocks.

The Barnes should give you all the penetration you need. I wouldn't stretch that caliber out to much past 300 yards on elk.

The Barnes starts penetration at 140grains and loses little weight.
The 150 Partition starts penetration at 150 and the front third quickly expands or wipes off entirely leaving you 100 grains to continue penetration.
In .270 caliber with elk, penetration is everything and my advice would be to maximize it with the X bullet.