TexasCHLforum.com

There is also the sight offset from the bore line to consider. In an AR with the original sights, that would be about 2.5 inches, so the bullet has to climb (bad term ,it's not actually climbing, it's just sighted in so that it gives the appearance of rising) until it intersects the bore line.

Since gravitational acceleration starts having an effect on the bullet the very moment it leaves the bore, it is falling at a rate of 32feet per second per second (not a typo) so thoeretically it might be possible to sight in your gun so that it took 600 feet for it to rise to the bore line (and this is a thing to strive for with very flat shooting high velocity rounds), but practically it's better to use the trajectory to your own advantage and improve chance for hits over a wide variety of distances.

So, with the 2.5" offset and the bullet crossing the bore line going up at about 50 yards, at every range from zero to 50 yards the shot will be slightly low (2.5" at the muzzle and reducing to 0 at 50 yards) . Then from 50 to 200 yards (give or take some wind and stuff, this is a good thing to test for) the bullet is up to about 6" above the bore line, and then it drops back below, falling to something on the order of 12" and more by 300 yards. The trajectory is a reducing radius curve, with the bullet slowing down and dropping faster due to gravitational acceleration until it finally hits the ground. Sighted in this way I can get reliable hits on a man sized target, or I could if I could see that far and not shake so much, right out to the maximum effective range of the round fired.

The sight offsets for my Garand and Springfield are much smaller, and the trajectory of those relatively heavy and slow moving bullets (RELATIVELY!) is a huge curve in comparison and necessitates a whole different ballistics table.

And of course each load will produce different ballistics, so the best thing to do is start with a table for a meatball approximation and work slowly to your desired point.

These same "rules" apply to handguns also, they just do it at shorter ranges.
-------------------------------------------------------------------------------------

Having said all that, the same "rule" would apply no matter what sight you were using, making me thankful that I put so much effort into making sure that my iron sights and HoloSight were co-witnessed within the bounds of human effort.

Don't take any of the above to indicate that I am some sort of super marksman, I have done a lot of training and studied guns most of my life, but the difference between theory and application can amount to a very large gap.

My HoloSight failed at the start of our three gun match yesterday, I found myself real happy with my co-witness Mangonels - they flipped right up and I was shooting great groups with them all day.

Next time I make sure I have fresh batteries in the HS before the match.

I set my sights point blank at 200, which puts them right on at 50, lower closer than 50 and higher from 50 to 125.