I also like the 50m zero for it's relatively flat trajectory throughout the various distances.
You might want to learn how to boresight, it's easy and will save you ammo. Google search should have lots of tutorials. They have lasers and other fancy gadgets that help but IMO you don't need them, the goal is to get on paper so doing it by eye is good enough. If you have a spotting scope or some other magnification that helps a lot too as it's real hard to see the holes at 50m+. You'll be able to make adjustments without having to wait for a cease fire to walk to your target.
Good suggestion on bore sight. I use a laser bore sight, but an AR is easy to do with just a point of reference, some way to hold the upper steady, and some patience.
Separate the upper from the lower, make sure the iron sights are flipped up, and use a gun vise, sandbags, etc. to hold the upper steady.
Find a point at about 50 yds away and, looking through the barrel, center the point you are aiming at inside that view through the barrel.
Then, look through the sights, making sure the upper stays in the same position, adjust as needed to align the sights on the target point. You'll want to recheck the barrel is still on target if you move the upper making sight adjustments.
When the aim point is centered through both the bore (barrel) and the sights, you should be on paper at 50 yds.
Good luck!.