I zeroed my 16" AR-15 in at 25 meters just fine, however; when I went to shoot at 100 meters I couldn't hit the 6x9 paper. I could easily hit it with an AK. Not sure what I'm doing wrong. Stock was fully extended. I did not have my nose on the charging handle like I recently read I should have had (I think I had my nose on the charging handle when zeroing a while back). I'm having trouble getting used to the peep sights. I wear glasses on top of it and it makes it even more akward. Any tips?