I couldn't get the SSTs to shoot well out of my 7-08 as well. I have only tried one load combination so far, but it was a bust for sure. I'm not overly fond of their on-game performance anyways.
That is a picture of an SST recovered from the deer pictured below. The shot was 225 yards broadside, deer stood straight up in the air and went right over backwards sticking its antlers thru the snow and into the ground. They kill well for me, but don't retain much weight. I have to find that bullet and weigh it again, but it was a 139gr SST and I think its down below 80grains. Now.
The bullet was found behind the opposite shoulder while caping the buck out. If you look close you can see the mud stuck to the bucks left G2 where it stuck in the ground.