I use a Shepherd 6x18 V2 on my suppresed .308 sniper rifle. It has a dual reticle rang finding and bullet drop compensating system that works for both super and subsonic loads. It is set up for the supersonic loads but with a day on the range you can sight in your rifle with the sub ammo and only have to adjust for windage. Keep a log book of what range circle to use for your hold over and you can quickly switch between sub and supersonic ammo with no loss of zero. I have placed many shots at 1000+ meters with M118LR ammo and many shots with 170gr sub ammo at 400+ meters useing this scope. I plan on useing a Shepherd 3x10 P2 on my 300 whisper. You can get this scope that is calibrated for the 7.62X39 wich has identicle ballistics to the 300 whisper for supersonic loads. Check them out at
www.shepherdscopes.com