i just built a 16 car from m&a. it fires fine, everything works properly, but the sights seem to be off. i have a flip up sight on it now and went throgh the zeroing  at 25 yards, got a really tight group. i then centered  the shot group on the target. my problem is  any further than 30 yards (shooting supported w/ sandbag) shots seem to impact very high on the paper.can anyone point me in the right direction, am i doing this wrong or what? thanks in advance

25 yds is too close to zero an AR. Due to the large amount of distance between the sight line and the bore centerline you have to have the sights elevated inordinately to get the thing zeroed at 25 yds. Once you move to 100+ the thing will be shooting way high.  Re-zero at 100 and you should be good to go.

rj

A1 sights or A2 sights?

Try zeroing IAW the -10, www.ar15.com/content/manuals/

You can use the -10 25m zero for A1 sights or the IBSZ with the A2 sights. I'm at work right now and can't get the link for the IBSZ maybe one of the other guys can square you away.

If you want to zero the rifle at 25 yards your bullet point of imapct (POI) should be about 3 inches BELOW your point of aim (POA). This is because the height of the sights is about 3 inches above the axis of the bore. Then you set up your target at 100 yards and complete your final adjustments. At 100 yards you should have a POI about 2.5 inches or so ABOVE your POA.

This will ensure that your point blank range will be out to about 325 yards or so. Good luck. Charles.  

EDIT TO ADD: The flat top sights are closer to the bore axis, so, about 2 inches low at 25 yards would be OK.  

i'm using A2 style flip up sights on a flat top receiver, i will try all methods offered
thanks for the replies, this site is truly at a level above the rest.             ooooh rah!!

As promised: Methods of Zeroing

Compliments of the folks at The Maryland AR15 Shooters Site.