I have a Bushmaster Shorty with the fixed (A2) handle.  When you look straight down at the rear sight mechanism it appears to be twisted slightly counterclockwise, or pointing to the left if you were looking at it from behind.  It is spring loaded so when you twist it straight, it always moves back to the left.  Has anyone noticed this before?  Is that normal?  It is accurate enough at the 30 to 50 yards that I plink at.  

It's normal and has to work that way.
Jack

Normal, mine is the same way. It's spring loaded so it stays zeroed. It is accurate to beyond your abillity.[;)]

That is normal for a std. Bushmaster. Rock River Arms runs thiers with much less slop.

Match Shooters DCM get this fixed.

Thanks.

I wondered about this when I got my first AR and asked the same question on this site.
I thought it was a defect as well.
It just looks strange when you first see it.

Armalite's take on this:


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BACKGROUND: Customer calls have disclosed considerable confusion over the construction of the M16A2 type sight used on ArmaLite® AR-10B™ and M15™ series rifles.

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FACTS:

1. The rear sight of M16A2 rifles is spring loaded in such a manner that it tends to rotate counterclockwise, as viewed from above. This biasing is caused by a ball and plunger in the left wall of the sight base, which presses against a surface of the receiver and forces the base to rotate. This is a means of taking up accumulated slack in the parts of the sight. The spring loading insures that the sight is always in the same position, even if cocked somewhat to the side. Keeping the sights consistently in the same position aids accuracy.

2. Depending on the buildup of tolerances, the cocking of the rear sight may be quite noticeable. While this may be somewhat unattractive, it is intentional, and is supportive of good accuracy. All M16A2 pattern sights display this cocking to some degree.

3. Some manufacturers produce rear sights with a ball and spring in the right sidewall of the sight base to counteract the ball and spring in the left side. This is an error: duplicating the spring on the right side neutralizes the left side spring. Removing both sets of balls and springs would have the same effect.

4. ArmaLite® produces a National Match rear sight assembly which bears a rail on the front of the right sidewall of the sight base. This rail tends to reduce or eliminate the cocking of the sight base. In case of unusually tight parts, it may be necessary to reduce the rail with a file or stone.

5. ArmaLite® purposely machines and assembles the rear sight aperture of its sights with the flat surface facing the eye of the shooter. The common G.I. assembly has a curved surface facing the eye of the shooter. This "poor mans hooded aperture" suffers a serious disadvantage: the spherical surface reflects light into the eye of the shooter, no matter what the incident angle of the light. The flat surface does not do so.

In summary, neither the rotated angle of the rear sight nor the flat faced aperture are defective.

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You can always have it pinned if it bothers you, but that make it harder to disassemble the rear sight assembly. (usually just NM shooters do this.)

Setting up your A2 to use the IBZ seems to eliminate the rotation issue with some uppers...

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