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5/28/2020 10:18:12 PM
Posted: 12/28/2002 7:43:31 PM EDT
[Last Edit: 12/28/2002 7:50:42 PM EDT by Venerated]
It came this way from the factory. As you can see it is canted to the left. It doesn't affect the accuracy at all, but I think it should be aligned with the carrying handle. When I turn the assembly to the right to align it, it turns itself to the left again which tells me it's under spring tension. I've never removed an A2 sight. I have the parts diagram but I'd like to ask the experts before I go removing things. Maybe it can be aligned without removal? I'd really like to get this taken care of. Thanks much.

Link Posted: 12/28/2002 7:46:17 PM EDT
A true sight expert can tell you why, but I can tell you that is normal.  I just checked two A2 receivers and three det. carrying handles and they all exhibit a similar degree of "cantedness".


Link Posted: 12/28/2002 10:46:48 PM EDT
The rear sight has a detent ball and spring on the left side only.  This will cause the sight to twist and track the right side only. This allow the sight to track truer than if it was loose.
It is normal on a service rifle.

To have the rear sight straight with the carry handle, you would need to install a second detent ball, or have the sight tracking modified to a Match type rear that uses rods to track.

Granted that yours is slight bit more canted then some, it is still normal.
Link Posted: 12/29/2002 4:33:40 AM EDT
I'll be da*n, never noticed that on new/first AR15. Thanks for the explanation Dano523!
Link Posted: 12/29/2002 5:46:43 AM EDT
A second detent on the right side will not fix the problem.  That will make the orientation depend on the relative strength of the two springs.

The spring detent on one side is designed to keep the sight in tension against the receiver.  If you want to rotate the sight back, remove the sight body and have a welder put a bump on the lower right side where it contacts the receiver.  File the bump down to fit the receiver with the desired angle.

However, your best bet is to just ignore it.  If you notice, the sight aperture is at the center of rotation.  It may cause the peep hole to appear elliptical rather than round but it wont affect the point of impact to first order.
Link Posted: 12/29/2002 9:01:02 AM EDT
[Last Edit: 12/29/2002 9:14:53 AM EDT by Venerated]
So bottom line, if I were to remove the assembly and re-install it, the odds are it would remain the same.

What about shortening the length of the spring behind the detent ball by a [u]very small amount[/u]? To quote oldguy, "the orientation depends on the relative strength of the springs", which is true. Shortening the spring would reduce the amount of pressure and thus reduce the cant. Would this affect the assembly dramatically?  
Link Posted: 12/29/2002 10:13:36 AM EDT

The two detent ball and spring system requries the two springs to be tweak to acheive the desired effect.  The problem that you run into by welding a spot on the side, is that the spot will start to dig into the receiver.  A better idea would be to build up the entire side of the contact edge, then mill to the disired effect.

In regards to your question on the single ball system(stock), you want the right side to track the receiver as firmly as possable, this prevents sight wobble.
If you loosen up the spring, your sight will wobble all over the place.  

If you do feel compeled to have the rear sight straight, you could just paper shim it(match book), or have the sight modified to a match type guide rod system.

Link Posted: 12/29/2002 10:47:02 AM EDT
You're right. Better to shim it than start messing with the spring. I think I'm going to use a semi-permanent fix by building up a small ridge of JB Weld on the rear of the carry handle. I can file it to the desired thickness and remove it entirely if need be.

Hey thanks for all your advice guys. It's just one more reason why I live at this site.
Link Posted: 12/29/2002 3:21:12 PM EDT
Since you feel compelled to pull the sight, Here is the low down on pulling just the housing(leave the peep alone).

Start by driving out the roll pin just below the elevation knob.  A spring will drop out of the inside of the housing elevation screw {inside of upper receiver).

Then slowly start to turn the elevation knob counter-clock wise.  The housing will come up, and at the top, the spring and detent ball will want to pop out. Retain the ball and spring, then finish screwing the housing out.  The elevation knob should be left alone, so don't try to pull it out.

Once you have done your build-up, start by slowly screwing the housing back down.  Use a little grease, and insert the spring/ball back in the  hole and retain the two until the the upper receiver holds the two in place.  
Then get about three turns down on the elevation knob, and insert the pressure spring back in the housing elevation screw,  threw the bottom of the upper.  If you can find someone to help you hold the spring in while you punch the retaining roll pin in, it will save you from having to grow a third hand. The easiest way is to use a small punch, and hold the closest side of the spring to the roll pin to allow the roll pin to get over the top, then drift the roll pin over just short of the other side of the spring,then press down on the loose edge of the spring and drive the roll pin the last of the way.

Note: I have a U-channel tool(punch with a slot for the roll pin to go threw) that allows me to press the complete spring down and drive the roll pin straight threw.  Without the tool, just work one side at a time.

Hope this helps.
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