I own a Tikka T3X Compact .308 bolt action rifle for deer hunting the Northeast. It has a 20" barrel with 1:10 twist. I was shooting 1" MOA 150 gr. Sako Super Hammerhead lead core ammo which performed well on deer but has been discontinued. I would like to make a switch to all copper bullets such as Barnes TTSX or similar for more knock down power. The question I have is what grain would perform best for my situation where most shots are less than 100 yards - most are 50 yards or less? Any recommendations on factory ammo and what should I zero my rifle for? Any help would be appreciated. Thanks