I've done some penetration tests with various .358 bullets. At 100 yards, two of three sierra 225's shed their core and one out of three 225 Nosler BT shed its core. Both produced a decent wound channel.

I used a 225 sierra game king on a small 4x4 mulie. The distance was approx. 250 yards and MV 2500+ from my Whelen. The bullet fully penetrated its neck vertebre and exited.

I personaly like the standard cup and core bullets for deer. There is no dought that the 225 sierra will hammer one of your blacktail. If you think you need a premium bullet in the 358, then use the partition.