Im shooting a Remington LTR match 308. Im using a Nikon buckmaster 4.5 x 14 with BDCs. im using a standard scope base. Im shooting at 14 power from 100 to 500 yrds. Scope work awsome at these didtances. Problem is when I move to 600 yrds. I have to drop my power down to 4.5. The match Ive been...