Re: What distance is your zero?
The most common zero is probably 100 yards. But it depends on what type of shooting you are going to do and the intended use of your weapon.
I zero my semi-auto .308 at 100 yards, and my bolt .308 at 300 yards. The SA will be used mostly from 100 to 300 yards - holdovers or doping the scope is easy for those ranges. The bold is used for targets 300 to 600 yards.
Beyond 600 yards, I plan on purchasing a .338 LM and will zero that at about 500 yards and shoot that gun from 500 to 1,000 yards.
Pretty simple system for ME - your milage may vary. So you see, it all depend on what you want to do. I could zero the (future) .338 at 100 yards - but look at all the adjusting I would need to shoot out to 1000.
I recommend creating dope cards for all the various ranges no matter where you set your zero.