I recently purchased a 16 inch LMT complete upper with a F marked front sight and an LMT tactical adjustable rear sight.  The front and rear sights were set to factory stock levels for the sight in.  While at the range over the weekend I had to adjust the front sight post down around two or three complete turns just to get it on the paper at 15 yards (gun was shooting low at the factory set level where front site was flush with the post.  The front sight has not bottomed out, but i'm worried how much further it will have to go down so I can sight it in at 50 yards.  This seemed odd as I have never really had to mess with the elevation with my other AR (RRA) to sight it in at 50 (just adjusted the windage and left the front sight at the 'flush with post level').  I'm shooting factory Remington .223 rounds, so low powered ammo isn't the issue and the grouping of the shots is good.  Is adjusting the front sight elevation down several turns a regular "par for the course" in getting an AR sighted in at 50 yards (i'm only at 15 yards now)???

I've had to adjust the front post on all four of mine (2 Colts, a LMT, and the new DD).

At 15 yards you will need to adjust the front way down. Why are you trying to zero at 15 yards? If you zero to 15 yards you will be about 3" high at 50Yards and 7-8" at 100 yards. To zero
to 50 from 15 you need to bring the front post UP not down.
1) Sight in at about 1" low at 25 yards.




2) Check for zero at 50 yards.  Adjust as necessary.




3) Check for zero at 200 yards.  Adjust as necessary.




4) Return to 50 to re-check and make note of any offset.




5) Check for offset at other user-defined distances.
Trajectory should be within 2.5 inches from 0-200 yards.





ETA: You might want to watch this.