Re: 7mm bullets..?
I shoot a 7mm SAUM and it should have ballistics similar to your 280. I've shot a lot of 139 SST for easy white tail hunting where range is usually lees than 400 yards. Have had very acceptable accuracy(1 moa)and reliable performance on Midwest white tails.
I have better accuracy with 162gr SST and plan on using that on elk hunt this year(Dec 2014) in New Mexico. I think IMO that is one of the best all around bullets as far as expansion, stoutness and BC. But, I would not shy away from any Nosler 150-160 Accubond or Partition, Matrix flat based 160 or even the Sierra HP hunting bullet(not Match).
If you work up a load(or buy factory ammo) and are confident with rifle and combo, practice at various distances you expect to shoot, that is the most important.
Let us know how that "7mm" shoots.