I am wanting to hunt deer this year with my dads Belgium Browning Automatic 243. I think the gun is around 50 years old. I just ordered a 3x9x40 Leupold Marksman Scope to replace the Weaver 6 power scope with tip off mounts. Im not sure what the barrel twist is on this rifle. What Brand and gr. Ammo would you suggest for Whitetails. My shots would be 250 yards max for hunting , but i would like to practice out to 500 yards. Thanks for any suggestions!