There's a thread over in the hunting forum about a guy hunting barbary sheep with the 6.5x55 Prvi ammo. He was very impressed.
I hunt with my 140grn Sierra GameKing reloads in my 6.5x55, and my 139grn Hornady Interlock reloads in my 7x57. However, I've shot a lot of Prvi through targets with both. It is very accurate, powerful, and the brass is excellent. Certainly a lot better than the Winchester or Remington stuff you can buy. Haven't tried Federal in any of them, so I can't speak for it, but you can't beat Prvi for the price.