My X7 likes the 300gr Keith Nose from Precision Rifle. This bullet will open great at low velocity but has a poor BC for 150yd shots.
I am not sure the SST would be the best choice at low velocity, though I have seen the 200gr version open well at 300 yds where the velocity is way down so I wouldn't count it out.
I used to kill a ton of deer with the HTP bullet over 85gr Pyrodex, but I think the XTP is much harder.
I would recommend looking at some of Precision Rifle's offerings like the Extreme or something, decent BC for 150yds yet still all-soft lead.