Same Plane

[ra2bach]

what is meant by rear sights that are said to be "same plane"?

[JLSKIP]

Could you give some more information or provide greater context?

[bkb0000]

rear sight that fits?

as in, m4 rear with F FSB, rather than M4 rear with A2?

same plain...

perhaps sights are zerod parallel to the bore, rather than with an intersecting axis?

[Jay Cunningham]

The traditional A2 rear sight apertures are on different planes, i.e. the small aperture is adjusted to an elevation at 300m (I believe) as compared to the large aperture - hence the "0-2" on the large aperture.

[JLSKIP]

Or maybe same plane is referring to something like the dual aperture nature of the rear sight of an A2?

The_Katar beat me to it with a better answer and faster fingers.

[LOKNLOD]

The standard AR rear sight has 2 apertures. One with large hole, and one with small hole. The centers of the two holes are not at the exact same height over the bore of the rifle. This creates a slightly different line of sight, and therefore trajectory, for a given zero. The centerline of the small hole is slightly higher than that of the large hole. If you zero for point of aim at a given distance with the small aperature, then your point of impact with the large aperture will be lower at that distance. Likewise if you zero with the large aperture, it will be higher with the small aperture. ETA: as The_Katar pointed out, understanding the differences can make shooting at farther distances a little easier. Think of it as the small aperture having a built-in holdover for longer range shooting?

A same plane rear sight has the centerline of both apertures on the same plane, and therefore they share the same zero.

[ra2bach]

The traditional A2 rear sight apertures are on different planes, i.e. the small aperture is adjusted to an elevation at 300m (I believe) as compared to the large aperture - hence the "0-2" on the large aperture.

ahhhh, that's what I thought. I have two different folding rear sights and both have A2 style dual apertures. I remember this from my Highpower days but I never changed apertures as I had a diopter in the large ap.

now another question, if I may:

I just installed this sight on an upper with an F-marked front sight and I am shooting about 4" low at 25 yards with the disc on the front sight post level with the top of the sight tower (not the protective ears), and I'm gonna have to crank it down really far to get on paper at 100 yds.

is there a special rear sight to be used with F-marked front sights?

[ra2bach]

The standard AR rear sight has 2 apertures. One with large hole, and one with small hole. The centers of the two holes are not at the exact same height over the bore of the rifle. This creates a slightly different line of sight, and therefore trajectory, for a given zero. The centerline of the small hole is slightly higher than that of the large hole. If you zero for point of aim at a given distance with the small aperature, then your point of impact with the large aperture will be lower at that distance. Likewise if you zero with the large aperture, it will be higher with the small aperture. ETA: as The_Katar pointed out, understanding the differences can make shooting at farther distances a little easier. Think of it as the small aperture having a built-in holdover for longer range shooting?

A same plane rear sight has the centerline of both apertures on the same plane, and therefore they share the same zero.

yep, I got that. I was 95% sure that was it but I wanted to be sure.

thanks for the excellent explanation as I'm sure (hoping? ) I'm not the only one who need that clarification.

[JLSKIP]

ahhhh, that's what I thought. I have two different folding rear sights and both have A2 style dual apertures. I remember this from my Highpower days but I never changed apertures as I had a diopter in the large ap.

now another question, if I may:

I just installed this sight on an upper with an F-marked front sight and I am shooting about 4" low at 25 yards with the disc on the front sight post level with the top of the sight tower (not the protective ears), and I'm gonna have to crank it down really far to get on paper at 100 yds.

is there a special rear sight to be used with F-marked front sights?

Wouldn't you need to raise the front sight post if you are shooting low?

As far as I know, the majority of BUIS (Back Up Iron Sights) are the proper height when "deployed" and used in tandem with an F marked front sight.

[ra2bach]

Wouldn't you need to raise the front sight post if you are shooting low?

As far as I know, the majority of BUIS (Back Up Iron Sights) are the proper height when "deployed" and used in tandem with an F marked front sight.

no. you move the rear sight in the direction you want the shots to go, and the front, the opposite.

think about it this way - if the front sight is on the target but POI is low, raise the muzzle relative to the front sight. that would mean you are lowering the front sight post.

le capisce?