AR sighting issues (Irons, POI drops as range decreases)


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Hiaboo
October 18, 2008, 03:34 PM
I have a matech (I believe, the same thing that the m4 uses) rear sight that it has clicks for 200 to 800 yards? and a POF front sight that is like a ghost ring w/ post.

Anyway, It is RIGHT ON at 50 yards and 150 yards.. But when I go any where closer to the target than 50 yards, the POI drops.. at about 20 yards the POI is about 4 inches lower from the POA. at 10 yards it is 6...

I'm wondering why the hell is this happening? This doesn't happen with my 30-30 which is dead on at 50 and 150.. Neither w/ my other AR w/ a red dot.

It is a 14.5" CMMG upper 1/7. Using 62gr w. 25gr varget behind it.

I would like a better rear sight that's more suited for close range than the one I have. Suggestions..

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rcmodel
October 18, 2008, 05:10 PM
That isn't possible.

The AR has a very high sight line compaired to most any other rifle.

But even so, the bullet path simply cannot be on at 50 yards, or 150 yards, and 6" low at 10 yards.

With your Matech sight set on 200, a 200 yard zero, and 55 grain FMJ-BT bullet, the bullet path would be approximately:
Muzzle = 2.5" low
10 yards = 1.98" low
20 yards = 1.5" low
30 yards = 1.05" low
40 yards = .63" low
50 yards = .26" low
60 yards = .08" high
70 yards = .38" high
80 yards = .64" high
90 yards = .85" high
100 Yards = 1.02" high
125 yards = 1.25" high
150 yards = 1.17" high
175 yards = .76" high
200 yards = 0.0

Changing to another brand sight would have no effect one way or the other, as they will all have to be the same height for a 200 yard zero.

Are you shooting off a bench or hand held standing, or?

I'd suggest you bench test it, sight it in dead on at 200 yards, and see if the above trajectory doesn't prove to be pretty close.

rcmodel

Tarvis
October 18, 2008, 06:44 PM
RC described the bullets' path perfectly. The only way the bullet could be 6" low at 10 yards is if the sights are more than 6" above the bore or the bore and the sights do not intersect.

janobles14
October 18, 2008, 06:51 PM
get dead on at 25 meters and you should have a "battlefield zero" at 300 meters. use the front post sight to zero off of a centered ghost ring. the elevation and windage are used for in shot adjustment.

Hiaboo
October 18, 2008, 08:50 PM
I know that it should not happen but it is.... It does not matter if I'm offhand shooting or hav eit on the bench, it is right on at 50 and 150 yards but if I'm closer than 50 the POI drops down lower and lower the closer I get to the target using the sights. I invite you to try it! :-p

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