Hey I have been shooting for a little bit now. I haven't gone past 220 yards due to the limitations of my range. I have been shooting .06 hand loads in 155 hornady amax and 150 sierra soft point. I have noticed a lot of people shooting much heavier stuff than that. I just switched up the .06 for a .308. I want to start shooting for around 600 yards, and farther later, but just 600 and under for starters. Should I buy some heavier grain bullets or can I keep using the 150-155s? I have been doing alot of reading and I see SMK. What does that mean is it brand/type of bullet? I have also seen people using 168 and up. My new rifle is a 700 20" bbl and 1:10" twist.